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Many Z80 computers in the seventies and early eighties used the S-100 bus, into which you could plug many kinds of expansion cards.

Would it have been possible to plug suitably designed game cartridges into an S-100 slot? Admittedly most of the computers using that bus were designed as business machines and didn't have color graphics, but supposing you had one that did have color graphics?

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Short answer: Yes


Would it have been possible to plug suitably designed game cartridges into an S-100 slot?

Sure. After all, such a cart would be just another ROM/Memory board. Although, some configuration might be required to avoid address collision.

Admittedly most of the computers using that bus were designed as business machines and didn't have color graphics, but supposing you had one that did have color graphics?

Cromemco's TV Dazzler was already available in 1976. It got quite some publicity, I think I remember even a book about it back then. So colour wasn't as uncommon on S100 as people might believe.

There were several S100 systems offering out of the box colour abilities (like Poly88) - and even more when considering (home) computers that offered S100 as expansion boxes, like the Exidy Sorcerer, ok, B/W, but you get the picture.

The main issue here would not only be a non-game-console-like effort to configure a card (Address and I/O usage) but also the lack of a standard way to access various hardware - not to mention the merits of some abstraction layer. We all can rant a lot about MSFT and Windows, but it did provide a proper way to encapsulate even the most weird hardware, making old games run on new graphics cards (and vice versa ... well, ignoring the missing power :))

From a game system viewpoint, the S100 bus would have been a way expensive system. For one, the bus doesn't offer regulated power, but rather expects each card to have their own regulators. Very primitive, good for quick-starting a system, but expensive on the long run. Same for the board size. Cost goes with board size, and an S100 module needs to be at least as wide as the connector is. Mind you, there have been even VCS cartridges that tried to use odd shaped boards to minimize surface. It's a penny business. Even with such tricks like triangular shaped boards etc., they would cost several times what a standard VCS cartridge board was.

There's a reason something like this never happened, despite the zillions of developments done for S100.

  • While technically feasible, practical hurdles were probably insurmountable. Razzfahn mentions cost. Another problem would have been marketing the thing. There weren't that many S-100 machines in the first place, and not a lot who owned those were gamers. Plus, you couldn't really think of it as a "cartridge". It would have to be its own complete system on a board. S-100 had no standard to access keyboard or joystick, some systems only had I/O over serial ports -- often even the "video" was via a serial terminal. So video, control, and sound would need to be supplied by the "cartridge". – RichF Sep 20 '17 at 16:12
  • This is a good point - technically possible doesn't mean commercially viable. One possible solution is to not try to cater for existing systems, but to design a gaming standard that builds on the S100 bus. This would allow you to very quickly design the system, and benefit from development cost reductions by reusing existing modules. Long term, you'd struggle to compete with the companies that designed an entire cheaper but less flexible system from scratch, but in the short term you might be able to make a quick win. – Jules Sep 28 '17 at 15:07
  • Then again, S100 is at the core just the plain 8080 bus. So any 8080 design would do the same. All that's need for a basic game cardridge system is a memory interface. Whatever I/O is needed can be done memory mapped. A write signal mit be helpful, but many machines have shown that it could work without. Same goes for adding banking logic to the base system as this would reduce cost on the long run. then again, who would ever want more than 4KiB of ROM? – Raffzahn Sep 28 '17 at 16:48
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The S-100 bus was introduced in 1975 and the first processor cards available used the Intel 8080.

A large number of cards became available over time, including a variety of video interfaces, both monochrome and colour.

There were also a wide variety of memory boards. These cards included both RAM and ROM types. So yes, a ROM board with a game loaded in it would work in the same way as a more modern games cartridge.

There are enthusiasts out there for the S-100. Sites like S-100 Computers try to keep the bus alive. There is a lot of information on the bus signals, for example at Interface Bus which covers other bus types too.

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The Exidy Sorcerer did exactly that, it had a cartridge format known as "ROM-PAC" that was simply a subset of the S-100 pins arranged in a slot at the rear of the right side of the case.

This was a very interesting machine, IMHO, that tried to bridge the world between S-100 business markets and home computers. Essentially it was the processing and memory parts of an S-100 machine packaged into a typical home-computer style case. An expansion slot at the back allowed the backplane to be connected to an expansion chassis that gave it full S-100 slots and floppy disk support.

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    Not realy. The ROM-PAC is a subset of the Sorcerer internal system bus, which again is not an S100 bus. The S100 Bus unit motherboard carries quite some logic (21 TTL as a quick count shows - got two Sorcerer setups siting right next door :)) to transform the Sorcerers expansion bus into S100. The ROM-PAC carries signals that are not found on an S100, therefore its's not a subset. And yes, the Sorcerer is a nice machine. Now, if you look for home computer like machine with S100 as system bus, the SOL-20 would be first choice. – Raffzahn Sep 26 '17 at 20:51

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