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Single-Chip Processors Have Reached Their Limits

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This text was first revealed as “Design case historical past: the Commodore 64.” It appeared within the March 1985 subject of IEEE Spectrum. A PDF version is on the market on IEEE Xplore. The diagrams and pictures of chips, circuit boards, and screens appeared within the authentic print model.

Charles Winterble, then director of worldwide engineering for Commodore, gave the go-ahead for the chip effort, and Charpentier’s group labored pretty independently till each chips had been completed in mid-November 1981.

At a gathering with Charpentier and Winterble late that month, Jack Tramiel, then president of Commodore, determined to not proceed with the online game. As an alternative, he determined, the chips would go right into a 64-kilobyte residence pc to be launched on the Shopper Electronics Present in Las Vegas the second week of January 1982. The pc had but to be designed, however that was simply remedied.

In two days, the engineers laid out on paper the machine’s primary structure. Simply earlier than the brand new 12 months, they accomplished 5 working prototypes. Within the meantime, sufficient operating-system software program was copied and rewritten from the VIC-20 to provide satisfactory demonstrations of what the brand new machine might do. Following its enthusiastic reception on the Shopper Electronics Present, the Commodore 64 was rushed into manufacturing; quantity shipments started in August 1982 and have continued unabated.

Regardless of complaints about high quality management and the trade’s slowest disk drive, the Commodore 64 has been an unparalleled success, pushing quite a few its rivals out of the market. A part of the explanation for its success is the value, which retains falling—from $595 at its introduction to $149 at the moment, for which the patron will get graphics and sound equal to or higher than that offered by machines that price 5 instances as a lot.

Designing the following nice chips

Within the late Nineteen Seventies, MOS Know-how was a profitable semiconductor firm; its engineers had designed the favored 6502 microprocessor, and it manufactured a number of different solidly promoting merchandise. Commodore, a West Coast firm on the time, took over MOS in 1976—inflicting most of the MOS engineers to give up when their inventory was purchased at 10 cents on the greenback—however MOS was allowed to function pretty autonomously.

In 1979 and 1980, remembers Charpentier, MOS Know-how developed the 6510 microprocessor—a minor revision of the 6502 with an extra input-output port, the 6526 peripheral controller, a number of read-only reminiscence (ROM) chips, and a 4-kilobit random-access reminiscence (RAM) chip. At the moment, MOS was supplying tools to Atari Inc., General Electric Co., Hewlett-Packard Co., and quite a few different shoppers, in addition to to Commodore.

When the choice was made to design the most recent in superior graphics and sound chips, step one was apparent: to search out what the present high-quality chips might do. In assembling his design workforce, Charpentier recruited Robert Yannes, a younger engineer who had joined MOS in 1979 and had designed the VIC-20 at residence, from a spare prototype board. The workforce spent about two weeks researching comparable chips industrywide.

“We appeared closely into the Mattel Intellivision,” remembers Winterble. “We additionally examined the Texas Devices 99/4A and the Atari 800. We tried to get a really feel for what these corporations might do sooner or later by extrapolating from their present know-how. That made it clear what the graphics capabilities of our machine needed to be.”

The MOS designers freely borrowed concepts that they appreciated—sprites from the TI machine, collision-detection strategies and character-mapped graphics from the Intellivision, and a bit map from their very own VIC-20. They then packed as a lot of these concepts as they might right into a predefined space of silicon.

“Al [Charpentier] was given the liberty, inside a sure die measurement, to place in the whole lot he might, working backward throughout the measurement we deliberate. When he ran out of registers he stopped,” stated Winterble. “We outlined upfront the silicon measurement that might give a yield we had been prepared to dwell with; at the moment, a die measurement that was affordable in 5-micrometer know-how was lower than 200 mils. Then we prioritized the want checklist from what have to be in there to what ought to be in there to what we’d like to have, so the choices that had been wanted at varied factors grew to become pretty computerized.”

9 months to first-pass silicon 

For 9 months, Charpentier labored with two draftsmen and one computer-aided-design operator on the graphics chip whereas Yannes labored with two different draftsmen and one CAD operator on the sound chip. They lacked utterly the delicate design instruments of at the moment’s engineering workstations, however that they had one available design device discovered nearly nowhere else within the home-computer trade: a chip-fabrication line on the premises. With this, Winterble defined, a circuit buried deep contained in the chips might be lifted out and run as a take a look at chip, permitting thorough debugging with out concern for different components of the circuitry. David A. Ziembicki, then a manufacturing engineer at Commodore, remembers that typical fabrication instances had been just a few weeks and that in an emergency the captive fabrication facility might flip designs round in as little as 4 days.

The price of creating the Commodore 64: Nobody is aware of.

The price of creating the Commodore 64: Nobody is aware of. “I had no formal price range accountability,” stated Winterble, “apart from Jack [Tramiel] watching me. Jack stated that budgets had been a license to steal.” As a result of MOS Know-how’s fabrication facility was not working at full capability, the tools used for C-64 take a look at chips and a number of passes of silicon would in any other case have been idle. “We had been utilizing individuals who had been there anyway,” stated Ziembicki. “You waste somewhat little bit of silicon, however silicon’s fairly low-cost. It’s solely sand.”

Though customized chips are often thought of costly, the C-64 chips weren’t. Not solely had been growth prices absorbed in firm overhead, however there was no markup to pay, as there would have been inf the chips had been constructed by one other firm. And yields had been excessive as a result of the chips had been designed for a mature semiconductor-manufacturing course of.

The sound chip was designed with 7-micrometer know-how, cutting down to six in locations. (Against this, the customized chip for Atari’s Video Computer System, fabricated 4 years earlier, was constructed with 6-micrometer know-how.) Commodore’s video chip was designed with 5-micrometer options.

As a result of design time moderately than silicon was at a premium, the chips had been laid out merely moderately than compactly. “We did it in a really modular trend,” stated Yannes. For instance, he famous, “the usual approach of constructing oscillators is to construct one after which multiplex it till you have got as many as you want. We simply constructed an oscillator module and repeated it, as a result of that was a lot quicker than figuring out all of the timing for the multiplexer.”

“What was exceptional,” Winterble added, “was that 9 months later, after we got here out with the primary cross, it functioned aside from one unhealthy sprite.”

In November 1981, the chips had been full. The unique intent had been a sport machine, however at this level the personal-computer market was starting to look promising. At a gathering of Charpentier, Winterble, and Tramiel, the choice was made to go for a private pc. The subsequent option to be made, in accordance with Charpentier, was between a 16-kilobyte and a 64-kilobyte machine, because the customized chips had been designed to deal with both choice.

“Jack [Tramiel] made the wager that by the point we had been prepared to provide a product, 64K Rams could be low-cost sufficient for us to make use of,” Charpentier stated.

When the design of the Commodore 64 started, the overriding objectives had been simplicity and low price. The preliminary manufacturing price of the Commodore 64 was focused at $130; it turned out to be $135. The pc would use the identical case because the VIC-20 and the same-sized circuit board, to hurry growth. “That wasn’t even a call,” stated Charpentier. “It was simply frequent sense. When you’ve received a product that’s a winner, why change it?” To change from the VIC-20 to the Commodore 64, the manufacturing group had solely to make the cartridge slot smaller, change the colour of the case, and design a brand new label.

Moreover, as a substitute of designing for efficiency first and worth second, as many engineers are inclined to do, the small design workforce at Commodore had price in thoughts from the start. Yannes, for instance, had made financial system his credo when he was an impecunious high-school scholar in search of components to construct a sound synthesizer. “Anytime I design one thing, I need to use the minimal variety of elements doable. It’s a private problem. If there’s a spare [logic] gate in a gate package deal, I’ll work to eliminate all the package deal, as a result of in working with a sure variety of chips, I ought to have the ability to expend the whole lot that’s in them. The Commodore 64 was my try and construct absolutely the minimal system that might be constructed out of the video and sound chips put collectively.”

Comfortable New Yr 1982!

Within the consumer-electronics trade, new merchandise are historically launched to distributors, sellers, the press, and the competitors twice a 12 months—throughout the first weekend in January and the primary weekend in June, on the Winter and Summer season Consumer Electronics Shows (CESs).

“Once you labored for Commodore,” stated Yannes, “you at all times needed to have one thing for the Winter CES.” The C-64 didn’t have a lot competitors on the winter present in 1982. Atari was nonetheless sowing its 400/800 pc. Mattel launched the Aquarius pc, and Spectravideo launched its pc/sport machine, each with restricted reminiscence and capabilities.

Ziembicki recalled, “All we noticed at our sales space had been Atari individuals with their mouths dropping open, saying, ‘How will you try this for $595?’”

“We had been successful,” Winterble added.

After the present, Commodore, which had a fame for typically exhibiting merchandise that by no means reappeared, needed to get the 64 into manufacturing shortly. Only some design modifications had been made to prepared the machine for manufacturing. “What’s within the 64 functionally is what I wished,’ Yannes stated. “What’s within the sound chip is what I wished, and what’s within the video chip is what Al [Charpentier] wished.”

In reality, stated Ziembicki, “after it lastly received into manufacturing, we appeared again and requested, why did we hassle altering it after January? It wouldn’t have offered one unit much less, and we’d have saved some huge cash on growth prices.”

A few of the modifications had been pretty vital, however they could have created as many issues as they solved. The most important enchancment was to treatment “a hiccup” within the video chip, stated Winterble.

When Charpentier first designed the video chip, he defined, his purpose was optimum efficiency in each black-and-white and coloration. Earlier video chips, corresponding to these used within the Atari and the Apple, had a black-and-white frequency of seven.16 MHz—twice the tv color-clock frequency of three.58 MHz—however this might not squeeze sufficient characters on a line, and it additionally induced cross discuss between the 2 alerts, inflicting an object to shift barely to the left or proper on the display screen relying on its coloration. After the January 1982 CES, when he noticed that 40 characters wouldn’t fairly match onto a TV display screen, Charpentier sped up the black-and-white clock charge and made the 2 clocks utterly asynchronous. However because the coloration and black-and-white units of data had been continuously altering part relative to one another, “the colour transitions had been incredible, however there was an total swimming impact,” he recalled. The answer was to place a phase-locked loop into the system so the colour and the black-and-white data would have a relentless relationship. This, Charpentier acknowledged, was “a Band-Help resolution.”

And that’s what it appears like, in accordance with Craig Nelson, director of product growth for Epyx Pc Software program of Sunnyvale, Calif. “It’s a very elegant circuit,” he stated, “aside from the phase-locked loop, which is simply caught in the course of it.” (Commodore now says it has redesigned the chip to eradicate the issue.)

On account of the “Band-Help,” the colour data and the black-and-white data shift part by 180 levels in relation to one another on successive video fields moderately than altering part unpredictably. This conforms extra carefully to the Nationwide Tv Techniques Committee (NTSC) customary, which requires black-and-white data to have a clock charge that’s an odd harmonic of the color-clock charge, in order that the 2 robotically reverse their relationship each different discipline—one discipline in part, the following discipline out of part. (Within the NTSC customary, colours are decided by the part distinction between the colour sign and a coloration reference sign transmitted at first of every line.)

On the time the usual was developed, generally obtainable circuitry couldn’t utterly separate the black-and-white data from the colour: modifications in coloration would result in modifications in brightness and vice versa. It was to common these modifications out over time that the NTSC specified that the relative part reversal of the 2 alerts might happen on successive fields. The result’s extra pleasing coloration transitions, however the part shift makes stationary figures seem to jitter. The jitter is especially apparent on skinny vertical traces, like these in alphanumeric characters. However when the Commodore 64 was conceived, it was to be primarily a sport machine, not a pc.

Working a 5-micrometer-technology chip at an 8-MHz clock charge prompted it to dissipate quite a lot of energy—almost 1.5 watts. Not solely did the chip run quick, however to stop the colours from washing out, as that they had within the VIC-20, “we went to 12 volt to drive the heck out of the colour alerts,” recalled Winterble. “We knew we’d have a warmth downside.”

At this level Winterble made one other design repair—welding a small metallic tab onto the within of the lid of the shielding enclosure across the video chip. When the pc was assembled, the tab pressed in opposition to the highest of the chip package deal, forming a heat-conducting path and turning the shielding right into a warmth sink.

Some modifications that may have improved the machine didn’t get made within the rush to manufacturing. For instance, Yannes stated, the wires for the sound output on the printed-circuit board run alongside the wires for the video sign. In consequence, the sound output picks up an annoying 15,750 -Hz whine. Rerouting the circuit would have taken time, “and we had a board that labored,” he defined. “At that time, if you happen to had one thing that labored, you didn’t change it.” A circuit-board revision since then has rerouted these traces, Commodore stated.

However the designers did in reality change some issues that labored—together with one revision that degraded the machine’s efficiency.

However the designers did in reality change some issues that labored—together with one revision that degraded the machine’s efficiency. The unique design specified a high-quality radio-frequency modulator to transmit the sign to a tv set, however a less expensive modulator was substituted. “It was $6.25 to $6.50 for a superb one, and we ended up spending about $3,” Charpentier stated.

Winterble has a unique view of the $3 modulator: “The 50-cent modulator we had been utilizing on the VIC-20 wasn’t adequate,” he stated, “so we went to a dearer one.”

Digital design wasn’t the one tough space because the Commodore 64 went from prototype growth into manufacturing—the logistics posed a fancy downside. The C-64 was designed in Norristown, Pa., at MOS. The VIC-20 meeting line, which was to start making C-64s, was in Santa Clara, Calif. Because the C-64 went into manufacturing, Commodore was additionally opening a brand new meeting line in West Chester, Pa. There have been extra VIC-20 meeting amenities in Japan, the place the disk drive for the C-64 was to be manufactured. And the C-64 circuit boards had been being made in Hong Kong.

“It was a number of enjoyable,” stated Ziembicki. “The design individuals would choose an English screw. The manufacturing finish would choose metric. However they went with what that they had. Commodore manufacturing was excellent at making issues match whether or not they had been supposed to or not. Their constitution was ‘Ship ‘em’”

“It takes a really powerful individual,” defined Charpentier, “to say ‘I’m not delivery these as a result of they’re not so good as they might be’—particularly when individuals are clamoring to purchase them.”

​Adjustments proceed throughout manufacturing

The beginning of manufacturing of the Commodore 64 within the spring of 1982 didn’t sign an finish to the controversy. “The secret is to have the ability to resolve your issues if you are working,” stated Ziembicki.

One of many first battles, recalled Charpentier, was over the structure of the printed-circuit board. Commodore’s meeting plant in the USA used automated component-insertion tools, however its Japanese facility didn’t, and the 2 meeting strategies required totally different element spacing. In the long run, the board for the C-64 was laid out for automated insertion, and manufacturing was moved to a brand new plant in Hong Kong that had the automated instruments.

Issues additionally plagued quite a few the elements—switches, for instance. “You choose a change that’s listed as a client change,” stated Ziembicki. “You design it in. You name the producer and get an estimate that sounds affordable. Then California [the production division] desires 50,000 per week, however the producer says, ‘We are able to’t make that. It’s a client change, however we’re not geared for client portions.’ At that time, you’re hung up.”

Since Commodore had simply moved its engineering workers from California to Pennsylvania, communication between the design engineers and the manufacturing amenities was not excellent, Ziembicki defined. “It received to the purpose the place you couldn’t cease working even if you happen to didn’t get an answer—you’d simply proceed with the elements that you simply thought the manufacturing finish might get.”

And outdoors suppliers weren’t at all times dependable. “One offered an influence provide for engineering approval,” Ziembicki recalled. “It received permitted, after which the provider modified the design and didn’t inform anyone.”

Charpentier stated that his relations with the manufacturing group had been pretty agreeable. Winterble’s dealings with them weren’t almost as cordial, however he discovered this acceptable. “I personally needed to play the heavy on a number of stuff,” he stated. “Then Al would go in and do some good. That method eased a number of pressure—it was a technique to get issues accomplished.”

Essentially the most infamous downside was “sparkle,” a defect that prompted small spots of sunshine to seem on the show display screen. The issue was solved earlier than Charpentier left the corporate in September 1982, however stories of the defect continued nicely into the Christmas season, with press stories citing it for example of Commodore’s poor high quality management. Canny customers used it as an excuse to return completely good Commodore 64s whereas they had been below 90-day guarantee. Because the worth of the machine had dropped $200 within the two months following its introduction, this ruse enabled house owners to acquire a refund of the acquisition worth and purchase one other C-64 on the decrease determine.

Sparkle was extensively attributed to bugs within the video chip that was the center of the system, however in reality it was brought on by a ROM chip of which 3 million had been in service with no issues in different programs, together with the hit arcade online game Asteroids. Commodore engineers themselves first appeared for the issue within the video chip. It took them three weeks to identify the ROM chip because the supply of the defect, Charpentier stated. “The issue was a random occasion—it didn’t occur on a regular basis. We thought the video chip was for some purpose seeing the flawed knowledge. We didn’t even suspect it might be the ROM. Lastly we put the logic analyzer on it and tracked it down.” The ROM, which Charpentier and his group had designed years earlier, had a particular pre-charging circuit to make it run quicker, however the circuit made it delicate to spurious alerts. The video circuitry and the 6510 microprocessor alternated in controlling the system bus, and when management handed kind one to the opposite, voltage spikes had been typically generated.

“It simply occurred that we hit the precise timing,” Charpentier stated. “If the spike had been just a few nanoseconds shorter or longer, it wouldn’t have been an issue. The spike was simply broad sufficient that the ROM noticed it as a legitimate handle. It could ignore the following handle request and provides the video chip flawed knowledge.” Because the ROM contained the C-64 character set, the display screen show could be affected by random slices of characters.

Based on Nelson of Epyx, “This confetti interference-looking stuff on the display screen, glowingly known as sparkle, has a particularly un-nice property: it causes {hardware} collisions—the sprites consider it actually exists.” Because the sparkle was brought on by inappropriate knowledge fed to the video chip, it triggered the circuitry answerable for checking whether or not the movable show objects—sprites—had been overlaying background objects on the display screen. So software program that trusted collision sensing to manage the motion of objects on the display screen would go berserk when confronted by sparkle.

The bug within the ROM was corrected, though Commodore needed to depend on outdoors suppliers for some time because it ramped up its new manufacturing line. Solely the primary few hundred thousand items shipped had the defect. However, Nelson noticed, “it doesn’t matter to programmers that it was fastened. Our software program has to work in each machine on the market.” One of the best resolution for programmers, he defined, is to repeat the contents of the ROM into RAM, which is dependable. However this wastes 2 kilobytes of RAM.

​“A screw-up in my timing”

Along with the problem with the ROM, “I made a logic error,” Charpentier recalled. The error, which was corrected typically after Charpentier left Commodore, prompted the early C-64s to generate the flawed variety of clock cycles on every horizontal video line. “It was off by one,” he stated. “As an alternative of 65 clock cycles per line, I had 64.”

In consequence, the 180-degree part shift between the black-and-white and coloration data, which might have eradicated color-transition issues, didn’t happen. Relying on their coloration and the colour of the background, the sides of some objects on the display screen would seem barely out of line. This was corrected roughly 5 months into manufacturing.

However main edges are nonetheless an issue with the C-64. The circuitry that shows both sprite data or background data at any level on the display screen is usually gradual to reply and overlays the sprite on the background data solely after it has missed just a few pixels.

The C-64 designers weren’t the one ones revising their machine; even some assembly-line staff received into the act.

The C-64 designers weren’t the one ones revising their machine; even some assembly-line staff received into the act. Since testing coloration high quality robotically is just about not possible, assembly-line staff had been instructed to show a potentiometer that controls the colour and black-and-white alerts till they noticed coloration. As Charpentier recalled, the employees quickly found that in the event that they turned the potentiometer so far as doable, it resulted in saturated coloration—but it surely additionally worn out the black-and-white sign. A number of thousand computer systems had been shipped earlier than the assembly-line staff’ “revision” was seen; by then, some reviewers had been lambasting the C-64 for its “garish” colours.

​High quality nonetheless missing

Although these modifications have been made within the C-64 since its introductions, designers who write business software program for the machine wish to see just a few extra. One such change could be sufficient high quality management. “They don’t take a look at,” stated Nelson of Epyx. “I’ve opened up brand-new Commodores and located traces minimize. They clearly use an influence screwdriver to assemble the C-64, typically miss the screw, and chop the traces. How, would possibly you surprise, might which have handed closing inspection? Properly, these traces are hooked as much as the disk-drive connectors, which they clearly don’t take a look at.”

In hindsight, Charpentier referred to as one in every of Commodore’s errors “not coming somewhat nearer to high quality.”

One criticism voiced by designers of add-on {hardware} for the C-64 is that its minimalist design leads to undesirable interactions between components of the {hardware} and software program. For instance, the circuitry used to manage the joystick and the game-paddle port is borrowed as soon as each 1/60 second to scan the keyboard for keys which have been pressed. If the joystick switches are closed, the keyboard-scanning software program will report {that a} key has been pressed. Gadgets that connect to the joystick ports may cause unpredictable responses—an issue that might not happen if separate {hardware} had been used for the 2 capabilities.

One other flaw is the pc’s crude inner software program. The system comes up in Primary when it’s turned on. This can be a leftover from the times of the primary Pet pc produced by Commodore, which had no disk-operating system, since there have been no disk drives available then. “An honest disk-operating system wasn’t developed till Pet Primary 4.0,” Charpentier stated. The C-64 doesn’t use this superior model of Primary as a result of “it could have required extra ROM than we might put in.” As an alternative, the machine makes use of a much more primitive model of Primary, borrowed from the VIC-20.

“Software program wasn’t tangible—you couldn’t maintain it, really feel it, or contact it—so it wasn’t price spending cash for.”

Essentially the most evident omissions from the Commodore 64’s Primary are instructions to manage the sound and graphics chips. “There was by no means any intention that the system would have built-in software program to manage the graphics or the sound,” stated Yannes. “That was an apparent a part of the Commodore philosophy; you don’t waste cash on issues that make the product dearer and that almost all of consumers aren’t going to make use of.”

“Commodore has at all times paid lip service to software program,” Charpentier stated. “They do sufficient to get by after which depend on outdoors sources to fill the hole. Commodore was an extension of Jack Tramiel, and to him software program wasn’t tangible—you couldn’t maintain it, really feel it, or contact it—so it wasn’t price spending cash for.”

The C-64 designers had plans of their very own for modifications which haven’t but been applied. They used the VIC-20 case to shortcut growth, however they did have a brand new case designed that they supposed to substitute in eight to 10 months. “It was thinner in entrance and had extra of a wedge form to it,” stated Charpentier. “I at all times thought the VIC-20 case appeared clunky.” Just a few new options had been additionally to be added to the machine.

The truth that these modifications haven’t been made has probably not affected the success of the C-64, asserted Brian Dougherty, president of the Berkeley Softworks of Berkeley, Calif. “This machine has the most effective graphics-display functionality of something that has but been accomplished for a TV display screen,” he stated. “It got here sloe to being an superior system.”

​The albatross of the C-64: its disk drive

The one main flaw of the C-64 will not be the machine itself, however in its disk drive. With a fairly quick disk drive and an sufficient disk-operating system (DOS), the C-64 might compete within the enterprise market with the Apple and maybe with different enterprise computer systems. With the current disk drive, although, it’s hard-pressed to lose its picture as a toy.

“Enterprise-oriented software program doesn’t look nearly as good because it ought to on the C-64,” stated Dougherty, “not as a result of the bottom system isn’t adequate however as a result of the disk-drive entry is just too gradual; any enterprise software requires a number of disk entry.” And because the DOS is so weak and lacks options corresponding to the automated creating and sustaining of directories and conserving monitor of information, “it’s much more tough to develop enterprise software program” for the C-64, he added. “Anyone like Lotus [Development Corp., manufacturer of a popular integrated business-software package] is dealing with much more issue than they did creating software program for the IBM PC, as a result of the PC has an operating-system construction that simply doesn’t exist for this product.

“The essential input-output system in ROM is finished pretty cleanly, in accordance with operating-system ideas. All of the routines that have to be there are there, however there also needs to be a facility for robotically studying the primary monitor of the disk and booting a extra refined working system into reminiscence.”

The disk drive does in reality have a facility for robotically studying the primary monitor of a disk, in accordance with Nelson of Epyx, however as a result of it’s not documented, it’s not extensively used.

How did the Commodore engineers botch up the disk drive?

“The disk drive? What a gory story!”

“The disk drive? What a gory story!” Charpentier stated. “That needed to do with the one advertising and marketing enter we did settle for. Advertising stated the C-64 needed to be suitable with the VIC-20.”

The disk drive on the VIC-20, Charpentier defined, was a direct descendant of the drive on the Commodore Pet pc. “We had a parallel IEEE-488 bus for the Pet disk drive; and we used an odd format within the early days to be able to pack knowledge: on the outer tracks, the disk strikes quicker than on the internal tracks, so the information charge modifications to be able to pack extra knowledge on the market. It was a pleasant concept, but it surely was clumsy, in that you simply’re incompatible with everybody else. That’s the nut this all began with.”

The VIC-20 disk drive was designed in Japan, and the bus was modified from parallel to serial to economize. The drive could be very gradual as a result of the serial-interface portion of the interface controller (the 6522) used on the VIC-20 doesn’t work. In consequence, the 6502 processor sends out one bit at a time below direct software program management, moderately than sending a byte to the peripheral controller and letting it maintain clocks, knowledge, and hand shaking.

“We fastened the serial-shift register for the 6526 [the interface controller used on the C-64 to replace the 6522] however we couldn’t use it, as a result of the disk drive needed to be suitable,” Charpentier continued. “And, as a result of the processor within the C-64is turned off for 40 microseconds each 512 microseconds, it saved lacking the interrupt alerts that management the disk interface. The answer: gradual the drive down even additional.”

Velocity was the one issue that would have been modified with out incurring the price of radical modifications within the disk drive; if the C-64 designers had been in a position to forgo VIC-20 compatibility, they might have accomplished significantly better. And ultimately, after all, the C-64 was not suitable with the disk drive of the IC-20 anyway.

“All of it stemmed from the 6522 serial interface not working,” Charpentier concluded.

Different producers are attempting to unravel the disk-drive downside of the C-64. Some are promoting their very own disk drives to be used with the C-64, however they’ve discovered it tough to interrupt right into a market that Commodore controls. Others are promoting applications that may be loaded into RAM to hurry up disk-transfer charges, however this selection applies solely to make use of of the C-64 for programming in Primary; prepackaged software program loaded into the system knocks the applications out of RAM. Epyx has launched a ROM-based program to hurry disk switch fivefold. Based on Nelson, this system will work with any disk-based software program. “That’s doable,” stated Charpentier. “The C-64 disk drive has its personal microprocessor and reminiscence, and you may ship data to it to alter the working system and to hurry up the serial-bus protocol.”

The usual software program for the C-64 disk drive can learn a 256-byte sector each 2.5 revolutions of the disk, or 512 byes per second. Programming methods utilized by Epyx have yielded switch charges of as much as 2.5 kilobytes per second. (Amongst different gradual disk drives, Atari’s 810 transfers 1000 bytes per second, and the Apple II disk drive runs at a most of 15,000 bytes per second.)

Intelligent design shaves pennies

The Commodore workforce had labored laborious to make sure a low preliminary manufacturing price for the C-64. Vertical integration helped preserve components prices down, and Winterble vetoed concepts for added options. The designers themselves believed in counting pennies; Charpentier stated he had discovered quite a bit” from Jack Tramiel, who was “an actual stickler for price. We agonized over each transistor.”

With a manufacturing price of $135 and a retail worth of $595 at its introduction, the Commodore 64 would have a retail markup comfortably above the trade customary of 1 to a few (maybe one to 2 when volumes climb). However Commodore has continued to search out methods to scale back each the retail worth, now $149, and the manufacturing price, believed to be between $35 and $50 at the moment.

Commodore wouldn’t affirm this price determine. Dougherty of the Berkeley Softworks estimated the prices of C-64 components, base don his expertise at Mattel and Imagic.

  • Three ROMS at $1 every.
  • Eight dynamic Rams at $1.85 every.
  • SID (sound) chip and VIC (graphics) chip at $4 every.
  • RF modulator package deal, $3
  • 6510 microprocessor, $1 to $2
  • A handful of TTL, buffers, energy regulators, and capacitors for a complete of $5
  • Keyboard, lower than $10
  • PC board, $1 to $2
  • Plastic case, $1 to $2
  • Energy provide and miscellaneous connectors, $5 to $10
  • Packaging and handbook, $1 to $2

In additional cost-cutting strikes, Commodore has changed the TTL with cheaper customized chips and has discovered methods to extend yields on the sound and graphics chips.

Not all cost-cutting steps had been with out detrimental impact on the system. The 6567 video chip was initially packaged in ceramic, despite the fact that plastic is less expensive. “We tried all types of issues,“ Charpentier stated, “copper-lead frames, metallic inserts within the package deal, and an ungodly variety of different issues to get a plastic package deal, as a result of a ceramic package deal could be very costly. However we couldn’t discover a package deal that ran cool sufficient. Earlier than I left Commodore, I listed some concepts to scale back the facility, however half of the chip was nonetheless working at an 8-MHzclip. With out a main redesign, you could possibly not get the facility out.”

The design workforce was autonomous—they did their very own market analysis, developed their very own specs, and took their child proper up by way of manufacturing.

The chip is now encased in plastic. Commodore engineers stated that along with redesigning the chip, they’ve developed a plastic package deal that may dissipate warmth in addition to ceramic.

Because the change to plastic packaging, quite a few new issues with the C-64 have been reported—issues which might be machine-specific or temperature-dependent. One failing that’s extensively recognized all through the software program trade is an inclination for the chip to lock up when a program switches graphics modes—from displaying a bit map to displaying characters [see sidebar, “A Rich Collection of Graphics Modes”]. “A sport we had been producing began to fail on the manufacturing line,” stated Nelson of Epyx. “Then we’d take a look at [defective disks] once more they usually’d work. It trusted which machine we put them on and what the temperature was.” Charpentier speculated that some circuit traces had been left floating within the authentic design; poor processing and excessive working temperatures would stress chips to the failure level.

One other downside that has begun to emerge in some C-64s is defective horizontal scrolling of bit-mapped screens. In a latest evaluation of the Summer season Video games, an Epyx sports activities sport for the C-64, the San Jose, Calif., Mercury News criticized the “flashbulb impact” noticeable throughout the swimming occasion. That, in accordance with Nelson, will not be an “impact”—the C-64 utilized by the Mercury Information reviewer merely doesn’t do horizontal scrolling correctly.

The liberty ended

Though the machine has its flaws, the designers of the Commodore 64 consider they got here up with many vital advances due to the liberty they loved throughout the early phases of the challenge. The design workforce was autonomous—they did their very own market analysis, developed their very own specs, and took their child proper up by way of manufacturing. However as quickly because the manufacturing bugs had been labored out and Commodore knew it had a winner, the company paperwork, which till then had been on the West Coast coping with the VIC-20 and the Pet pc, moved in.

“At that time, many advertising and marketing teams had been coming in to ‘assist’ us,” Winterble recalled. “The subsequent product definition was going to be thought up by one group, and one other group was to be answerable for getting issues into manufacturing, and Al’s group would do R&D on chips solely.”

“When you let advertising and marketing get entangled with product definition, you’ll by no means get it accomplished shortly,” Yannes stated. “And also you squander the power to make one thing distinctive, as a result of advertising and marketing at all times desires a product suitable with one thing else.”

Charpentier summed up their frustration: “Once you get many individuals concerned in a challenge, all you find yourself doing is justifying your self. I knew the Commodore 64 was technically nearly as good and as low-cost as any product that might be made on the time, however now I needed to hearken to advertising and marketing individuals saying, ‘It received’t promote as a result of it doesn’t have this, it might’t try this.’

“The liberty that allowed us to do the C-64 challenge will most likely by no means exist once more in that atmosphere.”

​Postscript (as of March 1985)

Of the unique Commodore 64 design workforce, solely Robert Russell stays at Commodore; he’s at the moment a design supervisor. The remainder of the workforce—Albert Charpentier, Robert Yannes, and Charles Winterble, together with David Ziembicki and Bruce Crocket, who helped debug the challenge and produce it into manufacturing—left Commodore within the spring of 1983 and fashioned the corporate Peripheral Visions. Their plan was to design one other pc. To acquire working capital, they took on a contract from Atari—to design a keyboard for the Video Pc System, which was previewed however then, because the videogame market crashed, by no means launched. Peripheral Visions was sued by Commodore, which stated the VCS keyboard was a challenge that belonged to Commodore. At this writing, the swimsuit had not been resolved.

Peripheral Visions has been renamed Ensoniq and can quickly launch its first product, a music synthesizer. Albert Charpentier is at the moment vice chairman of engineering at Ensoniq, Bob Yannes is senior designer, and David Ziembicki is supervisor of manufacturing management. Charles Winterble left Peripheral Visions and is now group vice chairman of electronics at Coleco Industries Inc. of West Hartford, Conn. And Jack Tramiel is at the moment chief government officer of Atari Corp., the corporate that was Commodore’s chief competitor within the home-computer market earlier than dropping almost a billion {dollars} in competing in opposition to the C-64.

To probe additional

Pc bookstores carry a big selection of books on the C-64. Amongst these advisable are
What’s actually contained in the Commodore 64, by Bilton Bathurst, revealed by DataCap of Feneur, Belgium, and The Anatomy of the 1541 disk drive, by Lothar Englisch and Norbert Szczepanowski, revealed by Abacus Software program of Grand Rapids, Mich. Pc magazines corresponding to Inventive Computing and Compute! evaluation software program and publish applications that run on the C-64. The Commodore 64 itself will be discovered at most massive retailers.

How Programmers Exploited the C-64 {Hardware} (Slideshow)

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A Synthesizer on a Chip

“I’d labored with synthesizers, and I wished a chip that was a music synthesizer,” stated Robert Yannes, the sound-chip designer and programs architect for the Commodore 64. He started engaged on the chip within the spring of 1981, assisted by two draftsmen and one CAD operator. “No person else had a good suggestion of what we had been doing,” he stated. “Past primary analysis, which I’d been doing since highschool, the precise design took solely about 4 or 5 months.”

The key variations between his chip and the everyday videogame sound chips, Yannes defined, had been its extra exact frequency management and its impartial envelope for shaping the depth of a sound. “With many of the sound results in video games, there may be both full quantity or no quantity in any respect. That actually makes music not possible. There’s no technique to simulate the sound of any instrument even vaguely with that type of envelope, besides possibly an organ.”

Though it’s theoretically doable to make use of the quantity controls on different sound chips to form the envelope of a sound, only a few programmers had ever tackled such a fancy activity. To make sound shaping straightforward, Yannes put the envelope controls in {hardware}: one register for every voice to find out how shortly a sound builds up; two to find out the extent at which the word is sustained and how briskly it reaches that degree; and one to find out how briskly the word dies away. “It took a very long time for individuals to know this,” he concluded.

Yannes additionally put a lookup desk within the {hardware} to transform knowledge from musical notes to the equal frequencies, however that required extreme silicon. “I took that out,” stated Charles Winterble, who was worldwide-engineering director at Commodore throughout the C-64 design.

The exact capabilities of the sound chip are usually not clear even at the moment, largely due to incorrect specs having been written when the chip was first designed. “The spec sheet received distributed and copied and rewritten by varied individuals till it made virtually no sense anymore,” stated Yannes. An instance of the defective documentation is the declare that the chip can logically AND a number of waveforms. The chip can produce both a triangular wave, a sawtooth, or a sq. wave, relying on which bit is ready in one in every of its management registers. “There isn’t a interlock to make it possible for if one bit is on, the others are off,” Yannes stated. “That will have taken an excessive amount of silicon.” So if multiple waveform is elected, the inner notes of the output multiplexer are discharged, and what emerges is the minimal of amplitudes.

One other error within the spec sheet issues the on-chip filters. “The filter was the very last thing that was labored on,” Yannes acknowledged. “I ran out of time. The pc simulation stated, ‘This won’t work very nicely’—and it didn’t.” The filter might have been mediocre, however the equations describing the way it labored had been simply plain flawed, Yannes remembers. “They didn’t hold collectively. Nobody gave me an opportunity to right them.”

Confronted by these incorrect equations, most software program designers use solely the sound chip.

A few of the Japanese programmers who wrote early sport software program for the C-64 took a unique strategy, Yannes famous: “They wrote it in accordance with the spec. It didn’t matter to them whether or not one thing labored or not. In consequence, applications made sound results you couldn’t hear.”

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