Questions tagged [s-100]

The S-100 (later the IEEE696) bus is a backplane standard introduced in 1975 supporting configurable card types.

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trying to debug old 1979 Micropolis 1016-2 floppy controller issue

I have an old IMSAI PCS-80/30 S-100. It runs Micropolis MDOS 4.0. I have Micropolis 1016-2 single drive (doesn't seem to read or write), Micropolis 1043-2 dual drive (reads sometimes when the moon is ...
Greg's user avatar
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Anyone up for decompiling some 8080 code for Kaleidoscope?

I came across a series of blog posts about Kaleidoscope, a demo program for the Cromemco Dazzler graphics card. The series implements an emulator for the system so that it could run this code again, ...
Maury Markowitz's user avatar
8 votes
2 answers
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Weird power lines for S-100, why no 5V?

In answering another question here on the S-100 bus (from my admittedly less-than-perfect recall), I wonder why the bus supplied 8 and 16 volt signals, relying on the boards to regulate this down as ...
paxdiablo's user avatar
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Why 18 expansion slots on the Altair 8800?

The Altair 8800 had a backplane with 18 connectors for S-100 cards. Why was the number 18 particularly chosen? It is fairly common for a computer to have the number of expansion cards be a power of 2,...
DrSheldon's user avatar
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Did anyone ever put half a megabyte of memory in an Altair?

The Altair 8800 typically, at least in the early years after its release in 1975, operated with no more than a few kilobytes of memory, for the excellent and sufficient reasons that memory was ...
rwallace's user avatar
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Did any S-100 cards have multi-byte peripheral registers?

This question asks about endian issues of the S-100 bus. A peripheral card that has a register larger than one byte (e.g. a 16-bit or larger word) would need to be read/written by more than one ...
DrSheldon's user avatar
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Did 68000 on S-100 have any problem with being big endian?

The S-100 bus was extremely versatile; originally designed for the 8080, computers using it had no trouble with the Z80 as a drop-in upgrade, and it even went to 16-bit with the 8086. To my surprise, ...
rwallace's user avatar
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Why did the Altair use 100-pin edge connectors?

The Altair 8800 was based on what came in later years (much to the displeasure of MITS) to be known as the S-100 bus, because it had 100 lines, because MITS found 100-pin edge connectors were ...
rwallace's user avatar
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11 votes
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How many cards could you put on an S-100 bus?

The S-100 bus was something of an industry standard in the 1970s, for 8080 and Z80 computers built on a backplane design. It was invented with the Altair 8800, which apparently provided 16 or 18 ...
rwallace's user avatar
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How was the 8 to 16 bit transition of data lines managed for S-100

The S-100 bus had 8 data lines, logically enough since it was originally used with the 8080 and then Z80 CPUs. However, it actually had two sets of 8 data lines. The reason why is discussed in Why ...
rwallace's user avatar
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Can anyone help provide more information regarding an operating system called I/OS by Infosoft in the early 1980's?

The title pretty much says it all. I'm looking for information about an operating system called I/OS by a company called Infosoft in the early 1980's. I think it might have been a CP/M variant and ...
Geo...'s user avatar
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Why were the data lines of the original S-100 bus unidirectional?

The bi-directional 8-bit data bus of the Intel 8080 was split into two unidirectional 8-bit data buses. Later these two 8-bit busses would be combined to support a 16-bit data width for more advanced ...
DrSheldon's user avatar
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Can S-100 cards attach to the ZX machines?

S-100 was, as I understand, a very popular way to connect various computer equipment together in the past. Also, from what I understand, S-100 closely matches the same signals as the Intel 8080, as ...
Omar and Lorraine's user avatar
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Intel 8080 and Altair 8800. 256 I/O ports, but only 7 free RST (interrupt subroutines) — how does it work?

I have seen the video Altair 8800 - Interrupt Acknowledge Cycle and I have a few questions (I have read Wikipedia’s Intel 8080 article, the Altair 8800 Operator's manual, Charles Petzold "Code&...
MiniMax's user avatar
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Differences between 4k, 8k and Extended Altair BASIC?

Various histories state that there were at least three versions of Altair BASIC, 4k, 8k and Extended - plus modifications like Disk. I've found some listings of the 4k, but does anyone have a short ...
Maury Markowitz's user avatar
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1 answer
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Is S-100 alive?

1) Is S-100 still supported or available for serious home brew? Does anyone still actively sell new boards, cases, designing, support, etc? If not, then about what year did S-100 development stop? 2) ...
jwzumwalt's user avatar
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Game cartridges on the S-100 bus?

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 ...
rwallace's user avatar
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3 votes
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How many CP/M machines ever shipped? [closed]

How many machines for which CP/M was the primary operating system (so not counting the Commodore 128) ever shipped? I would also be interested in knowing how many S-100 machines ever shipped. I get ...
rwallace's user avatar
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S-100 bus and device drivers

It is said that the S-100 bus provided a standard hardware format for expansion cards across many models of computers, including ones using different system software and even different CPUs. Having ...
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