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15

The standard (IEEE 696) is available here Section 1.1 defines the scope of the standard as Data exchanged among the devices is digital. A maximum of 22 devices are interconnected. The total transmission path length does not exceed 25 inches The maximum switching rate is 6 MHz.


12

As Wikipedia says (S-100 bus): "(Author) then looked for an inexpensive source of connectors, and he came across a supply of military surplus 100-pin edge connectors. The 100-pin bus was created by an anonymous draftsman, who selected the connector from a parts catalog and arbitrarily assigned signal names to groups of connector pins." So the ...


12

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 ...


12

Like most busses of its time, you had to write your own software to communicate between the cards. The term device driver wasn't widespread at the time, but that is what you were writing. The S-100 bus (IEEE696), with its standard 100-pin socket could support a number of different cards. While it was common to have a processor card, memory card and ...


11

Yes, there are still a few communities using and developing S-100 boards. A good place to start is the S100 computers site, which lists a number of new S-100 boards which can be ordered and used to build new S-100 systems. The corresponding forum is very active. I think the most popular S-100 configuration is still a Z-80 with CP/M, albeit with newer ...


9

And I found the answer only moments later when I came across the original manual. The difference is that the 4k version (mainly) did not have strings (!!), lacked a number of math functions (ATN, etc), logical operators (AND, OR) and PEEK/POKE. UPDATES: And a short form of the differences can be found in the original MITS brochure. Although no specifics ...


8

Can S-100 cards attach to the ZX machines? That calls for a clear Yes, But :) S-100 closely matches the same signals as the Intel 8080, as does the Z80 which the ZX Spectrum etc., have. Adding a basic S-100 bus bridge for the ZX80/81 or Spectrum would in fact be no big deal - only some money to spend for bus board, cage, PS and so on. It would become a ...


8

An important thing is that old-style expansion buses - that includes S100, als well as the PC ISA bus and various proprietary buses, had no enumeration capability - a computer system was not aware of what was installed in the slots unless it explicitedly tried using any of that hardware - and what I/O addresses it responded to. Neither could I/O resource ...


7

I have looked this video - Altair 8800 - Interrupt Acknowledge Cycle and have few questions (I have read wikipedia Intel 8080 article, Altair 8800 Operator's manual, Charles Petzold "Code" and few article on the internet, like this and didn't found answer yet): Maybe to start with the obvious: Not every device needs to be interrupt driven. Altair 8800 ...


6

[Preface: It might be more appropriate to read the S100 standard documents instead] The S-100 bus had 8 data lines, logically enough since it was originally used with the 8080 and then Z80 CPUs. Yes ... err no. The original Altair-bus was made only for the 8080 (and the Altair), while S100 is the later standardization removing some unclear points and ...


6

1 I/O port <> 1 hardware device 1 RST vector <> 1 interrupt from one device You have read the datasheet under false assumptions. There is no such thing as a 1:1 correlation between these concepts. Actually, I/O devices that hold only one single I/O port are pretty rare. A typical floppy controller, for example, the WD1772, has four registers (...


4

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 ...


4

Manassehkatz is correct about the bus. All components can see all bus activity. So each picks for itself which bus cycles to respond to; ordinarily IO accesses to a particular address or range of addresses. The 8080 has a very direct interrupt system — it'll read an instruction off the bus and execute it. In practice it's easier to make these single byte ...


4

The first page of the article Getting Compatible with CP/M implies it was an alternative name for Infosoft's TSA/OS, and was indeed a CP/M variant.


4

It's rather simple concerning the hardware. To operate the bus without the CPU (while plugged in), the databus needs to be separable from the CPU. That's why buffers are needed. While the processors direction signal (DBIN) could have been used for CPU initiated transfers, it would not be possible to use that when the CPU is halted in any state. Also a simple ...


3

How does this work from the endian-ness perspective? Endianness is for most parts a software issue. Hardware, especially memory is either agnostic to the way a word ist stored, or doesn't have any idea about units wider than a byte at all(*1). Basically all I/O on S100 is 8 bit wide - after all, continuing the use of existing peripherals was a main point of ...


3

AFAIK Mostek M/OS-80 was a licensed derivative of an Infosoft CP/M-compatible operating system. There is an M/OS-80 manual on bitsavers in this directory: http://bitsavers.trailing-edge.com/components/mostek/z80/


2

The chip has 256 I/O ports, rather than some smaller number, because it was just as easy to provide 256 ports as it would be to provide eight. The part supports eight restart vectors because the hardware to support eight was simpler than hardware to support more. Note that many I/O devices use a single interrupt but use multiple I/O register addresses (...


2

not quite an answer to the question: In our post-90ies and beginning-of-2000ies ZX practice, we were connecting ISA modems to ZX Spectrums here, used BBSes and FIDO via them (there is software for that, of course). Bus convertor was nothing more complex than /RD /WR etc. signals generator, address decoder and signal buffers. then the formal yes useless ...


2

A long time ago I worked on an Alpha Microsystems computer which was S-100 based little-endian, and while I was there we upgraded to a 68000-based system that had been wired (I don't know the details) to behave as if it was a little-endian system. So I can't give you details, but it is possible.


2

Buses like S-100 are "endianness-agnostic". They do not care about data and its order, they just transport desired content as CPU (or "master") asks. Endianness is "the CPU thing".


1

I have never seen any 16 bit I/O cards. There wasn't much business sense to build such, as it would have quite limited possible sales. (CPU)-Boards according to the IEEE standard for 16 bit access (*1) had to be able to turn any 16 bit request into two consecutive cycles to enable seamless interaction with 8 bit boards. Making a card requiring single cycle ...


1

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 ...


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