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138

Simple: Complexity. A 8088 had about 29,000 transistor functions, while an 8087 with 45,000 is almost double that. Integrating the FPU within the CPU would have made it three times as big, putting production at a >5 times higher failure rate, resulting in a price tag way higher than 3 times the CPU alone. More like 5-8 times. When closing in to what is ...


65

Caveat: It might be useful to distinguish between high volume low cost computers (like the mentioned CoCo) and low volume high cost machines (like Intel boards - or workstations). I assume the question to be rather about these high volume low cost machines. Why were chips socketed in early computers? There are several reasons: Most important: Chips ...


63

So these math chips (I assume you're talking about floating point units, such as the 8087 and other coprocessors) were not always/usually included in the CPU because they were not required by most users. When you don't need floating point maths, you also don't need the FPU, and that was the commonest case. So to make the CPU cheaper they leave it out. Then ...


50

Another point not addressed in the existing answers relates to the latency associated with accessing an external coprocessor. The first math coprocessors, while much faster than doing the same work on a CPU, still took many clock cycles to complete each operation. The overhead (bus cycles) associated with transferring data between the two chips was "lost in ...


45

After some more research, I believe I've stumbled across the real answer: The VIC-II and SID used a larger process node size because Commodore's fabrication line circa 1981 was uniquely positioned produce chips at that size at effectively no production cost whatsoever. Based on what I've read, here's my best guess at what Commodore's fabrication situation ...


38

It seems to me there are a number of factors involved, some of which have been addressed in other answers: design complexity cost (which largely results from the complexity) feature necessity time-to-market Regarding complexity, as Raffzahn explains, early FPUs were much more complex than the CPUs they complemented. This meant that they needed more ...


28

There were. A couple of examples are the Motorola MC6845 and the MC6847. These chips were flexible and allowed various resolutions and colors depending on how they were implemented. The MC6845 was used in the Acorn BBC Micro, the Amstrad CPC and the IBM PC MDA and CGA video adapters. The MC6847 was used in the Tandy TRS-80 [Model 1], the Acorn Atom, the ...


23

Ranger was to be the next generation Amiga, which the original West Coast Amiga engineers began working on in 1986-87, following the release of the Amiga 1000. Jay Miner improved the graphics chipset for Ranger to address the twin problems of chip (i.e. Graphics, Sound, DMA) RAM memory space and bandwidth in the Amiga 1000. The Original Amiga chipset (OCS) ...


21

The TIA chips were manufactured by a number of different companies, in a number of revisions over the years; the Atari Compendium’s page on the topic lists: American MicroSystems (“AMI” marking on the TIA) IMP Intersil MA (it’s not clear which manufacturer this is) Motorola National Semiconductor OKI Semiconductor Synertek TSU United Microelectronics Corp ...


20

The MOS 6502 (1 MHz) was introduced in 1975 for a price of $25. Then in 1978 MOS agreed to sell the 6502 (1.79 MHz) and an IO chip to Atari for $12 per set (because the production cost was $4). In 1977, the Zilog Z80A (4 MHz) was $65 for the ceramic package and $59 for the plastic version.


19

One factor is indeed better heat dissipation properties of the ceramic housing. In those times both Z80 and 6502 were NMOS and had considerable heat release, so better heat transfer properties of ceramic housing could help achieve higher ambient working temperatures. Second factor is temperature range. In most cases, temperature range of the chip is defined ...


19

The question should rather be: "What could it have been?" - It never made it into an existing machine. According to some Internet lore, Kelly would have been the A3000+'s/AA3000's RAMDAC (digital video memory to analog RGB converter chip) that Commodore was initially planning to develop themselves. According to the same lore, during the development of ...


19

One reason to use sockets at the beginning of a production cycle is to make it easier on the service technicians. At one company making computer terminals, the techs would identify a bad chip and then give the board to the rework person to replace. This destroyed the presumed-bad chip and risked damage to the board. Before the techs were familiar with ...


19

It's a ground wire. The way ICs were manufactured back then had the metal cover placed over the die as the last step, and grounding it helps protect the die from static shock and interference. If you look closely you can see the solder that bonds the strip to the die cover. If you check continuity you will find that both are connected to the IC's ground ...


18

One could just as easily ask why it was not extended to 64 bits, or even wider. Well, if you ignore backwards-compatibility and cost, yes, it could have been. I'll pretend we can ignore backwards-compatibility and concentrate on cost first. Making the data pathways 32 bit would immediately double the number of transistors, with a corresponding doubling of ...


16

Logic 6510: ~3500 VIC II: ? (est. 5000) 2x CIA: ? (est. 2000) PLA: ? (est. 1000) SID: ? (est. 2000) commodity chips: ~500? Memory 64K DRAM: ~526000 (one transistor per bit, one transistor per row per bus width) 512 B SRAM: ~25000 (six transistors per bit 20K ROM: ~160000 (one transistor or diode per bit) The bulk number goes to the RAM, 50,000 isn't ...


16

I designed a color graphics card for the Z80 ECB bus back in 1984 or so, based on the 6845. The 6845 was "just" a timing and addressing generator. It was meant for character-based displays. So it divided the display area in character cells. Each character cell could span some horizontal pixels (to be serialized outside of the 6845) and some vertical scan ...


15

In the Wikipedia article on Transmeta there's a good example for the Code Morphing process, taken from a PDF document (Wayback archived) with even more details: The operation of Transmeta's code morphing software is similar to the final optimization pass of a conventional compiler. Considering a fragment of 32-bit x86 code: add eax,dword ptr [esp] // ...


15

In short, 3 µm looks like it was available at the time, The questions are rather: to whom it was available and is it worth the investment. Processes aren't anything you'd buy from some supplier but develop in house. The fact that Intel got a 3 µm process does not translate to any other manufacturer being able to do so and more important doing so. ...


14

The Motorola MC6847, used in the TRS-80 Color Computer, or the Texas Instruments TMS9918 would be good candidates. Both were available in 1980, and could display 256x192 pixel colour images.


14

A lot of the time the answer is "not without difficulty": chips from 6502 machines tend to simply assume they have access to the bus every other cycle; you can't achieve that on a Z80 without stopping the clock every other cycle which would be hugely wasteful since memory accesses are only as-required. The Z80 devices tend to fiddle with the clock and/or use ...


13

MOS was renamed to Commodore Semiconductor Group (CSG) sometime after Commodore bought them in 1976. After Commodore folded in 1994, the CSG division was bought by its former management and renamed to GMT Microelectronics (Great Mixed-signal Technologies). They continued with design, manufacture, and marketing of analog and mixed-signal power management ...


13

DRAM access in general and page mode (*1) in particular are not CPU features, but depend on the DRAM controller. No matter if build by discrete components (like mulitiplexers and counters) or dedicated IC. Pagemode DRAM can be used with any CPU if the controller (access logic) used supports its features. No matter if it's an 8080 or a 68020. You won't find ...


13

There was a brief fad in the early eighties for what's called "Wafer Scale Integration". That is to say, producing an entire wafer of silicon for a single circuit. The best known example was Gene Amdahl's Trilogy Systems. A Wafer Scale circuit can be used to build a massively powerful computer system in a single component, but as wafers are almost never ...


12

The above answer gives prices for times close to the release of the chips and at dates of significant sales. But note that prices were effectively in freefall, and that every quarter year saw significant reductions in price around this time. The price at the start of 1978 is not necessarily the same as it was by the end. What we can see is that within 3 ...


12

The standard US Apple //e Video ROM was pin compatible with 2732 (4k) EPROMs, but some foreign models (UK, German, French, Italian) used a 2764 (8k) compatible ROM with two character sets. Your clone might be the same or it might be different - the best way is to try to decode the pinout using either a logic probe (while on) or even a multimeter (while off) ...


12

This simple answer is not enough room on a chip for the total transistor count given the limitations of the process technology of the day. As per Wikipedia on the Intel 8087: The 8087 was an advanced IC for its time, pushing the limits of period manufacturing technology. Initial yields were extremely low. This for the coprocessor all by itself. ...


11

A typical EPROM series of that period is the 27xx series. Today's DIL EEPROMs still use the same pin layout. Access time varied with models. Datasheets with exact dates are difficult to google systematically, but for example, an Intel 2764A-250 had a 250ns access time in 1983, while the 2764A-1 variant had a 180ns access time in1989. So the ballpark is "...


11

Like anything else, in the end, it was "ease of use" for some value of "ease" and "use". The primary motivator was performance, the specialized processors are just an extension of the maturity of micro electronics and CPU design. Recall that the original computer were just discrete components. Then, as the ICs evolved, gates out of transistors, and flip ...


11

For example, the VIC-II is a big complex chip for its time; at least in the early days, yield must have been significantly less than 100%. Not really, while the VIC-II had a transistor count a bit larger than the original 8µm NMOS 6502. Not a lot, but it was manufactured in a 5 µm process, resulting in a smaller size and higher yield. The 1981 65C02 had ...


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