S-100 kit building

[lynchaj]

I would like to know if there are S-100 computer building kits available.

In the early 1980's I used to be able to buy empty circuit cards for IBM PC clone computers, purchase the components, solder up the boards, test, and use them. I made a memory card and a floppy disk controller. A friend made an IBM PC clone motherboard the same way. It was inexpensive and a lot of fun.

Years later (early 1990's) I did something similiar building a VHF radio transceiver from Ramsey Electronics. I also built a Poor Man's Packet TNC adapter modem and attached it to my PC to do packet radio. It was by far the most interesting thing I ever did Ham radio.

I would like to do the same thing but building an S-100 based computer.

Do any companies sell just plain empty S-100 cards, motherboards, cases, etc? Something inexpensive that could be built up one component at a time.

If S-100 based kits are not available, where can I start with kit building a computer? I am not interested in just assembling ready made parts to form another clone computer like a P4 or Athlon. Ideally, it would run something like CP/M or linux and avoid the whole modern x86 type machines.

I saw the AltairKit.com website but $1499 is a bit steep to begin kit building.

Any suggestions?

Thanks in advance.

Andrew Lynch

[chuckcmagee]

I am pretty sure in our new "International" world that kits are no more. Why would someone buy a kit when for $1.88 at K-Mart they can buy the whole thing, put together, and working? Kits were a device to save money on labor costs. Now you can get 10 hour day for 50 cents.

That said, there are "Apple I" kits out there. Not sure how expensive those are.

[atari2600a]

There are members here that do this kind of stuff (for example, Thrashbarg), & the creator of the Altair reproduction kit (Grant) is an active member here.

Other than that (side the Replica I), your chances are slim-to-none of finding a good kit, let alone an S-100 kit, other than the Altair reproduction kits Grant provides for a pretty penny. (or rather a pretty 149900 pennies:p)

Every once in a while an S-100 card, mobo, case, etc... goes up on this forum &/or eBay though...

[dongfeng]

I've seen a few blank IBM prototype cards on eBay over the last few months.

[nige the hippy]

Hi i got a complete 8 slot backplane from Ebay US last month for about $12, (not worth the soldering hassle, and easier to get than the parts) other than that, as dongfeng says, look out for blank boards, or... design one yourself, with lots of pads, and power supply components and get a few made.

Go to a friendly local pcb supplier (and shop around because the differences in price can be huge) also say it's for yourself as a hobby, and you might be surprised about how cheap it can be. I recently got 10 double sided boards, about 4"X10" made by a firm I dealt with commercially, would have been about £200 but because it was for myself, it cost £70 including photoplotting etc, and they gave me a few spares too! That was a GOOD deal.

I would think that prototyping boards would not be as cheap, because of the large number of holes, but, food for thought.

[lynchaj]

All,

Thanks for the responses.

Based on the replies, it appears computer kit building has largely disappeared. I recall it being rather common in the late 1970's and early 1980's but that was a long time ago. It is a shame its gone but I can understand it.

I think my next step is to visit the local electronic surplus shops to see if they have any S-100 bus chassis. If no luck there, I will try eBay to see what is available.

Hopefully, more to follow. Thanks for your insights!

Andrew Lynch

[Bill_Loguidice]

I have an empty S-100 chassis and mainboard that I've been looking to populate, so I'll be interested in your experiences. This is not quite the same thing, but www.xgamestation.com has some interesting kits, though they're obviously more videogame-related, but is probably a lot of what you're looking for in regards to a challenge.

[Terry Yager]

EBay user 'frotz661' has been listing several P112 kits over the past few months. He doesn't have any up right now, but if you drop him a message, mebbe he still has a few left.

--T

[lynchaj]

Hi again,

Its been quite a while so I thought I would come back and post an update on this thread. I have a couple of questions as well.

Since I had no luck finding a S-100 kit to build, I decided to do some research at the library and on the internet. I decided to just make my own Z80 kit and build it completely from scratch. Basically, I built a unique Z80 circuit with SRAM/EEPROM/UART/PPI/RTC peripherals and it boots CP/M 2.2 from a ROM drive. It works great and has been a lot of fun.

I decided to implement a simplified ECBbus (European Common Bus) since S-100 did not appear to be a practical option at the time. ECBbus is very Z80 compatible and relatively easy to implement. I have built a bus tester peripheral card and am working on another peripheral card presently.

Question #1, are homebuilt computers such as mine an appropriate topic for the Vintage Computer Forums, and if so, where? I consider it a vintage design of new construction.

Question #2, does anyone know of a interface circuit to attach a Z80 bus (address, data, and control) to an S-100? I am considering building an ECB to S-100 "bridge" card which would allow the ECB based computer to access S-100 motherboard & peripherals. I think a simplified S-100 Z80 circuit could be modified to work. Ideas?

Thanks!

Andrew Lynch

[Thrashbarg]

I decided to just make my own Z80 kit and build it completely from scratch. Basically, I built a unique Z80 circuit with SRAM/EEPROM/UART/PPI/RTC peripherals and it boots CP/M 2.2 from a ROM drive. It works great and has been a lot of fun.

Whoa! Pictures please!

Q1, I don't see why not. It's vintage computing technology we're dealing with here after all. I talk about my projects here.

Q2, Have a look at the schematics for Z80 S-100 CPU boards. There are a few at Dave Dunfield's site, specifically http://www.classiccmp.org/dunfield/s100c/index.htm . Hopefully that'll give you some ideas.

[lynchaj]

Whoa! Pictures please!

Q1, I don't see why not. It's vintage computing technology we're dealing with here after all. I talk about my projects here.

Q2, Have a look at the schematics for Z80 S-100 CPU boards. There are a few at Dave Dunfield's site, specifically http://www.classiccmp.org/dunfield/s100c/index.htm . Hopefully that'll give you some ideas.

I will post some pictures tonight. One caution though, Test Prototype is not a pretty thing to look at as it is built with stacked prototype boards with point to point wiring attached to an ECBbus. It is basically a fuzzy ball of wires intermixed with ICs and prototype boards. ;-)

There are some pictures posted on the ALPACA_designers Yahoo! Group http://groups.yahoo.com/group/alpaca_designers/ but you have to join the group to see them. The pictures are in my files directory along with some design information.

Q1, OK Thanks. Just trying to stay on topic.

Q2, Thanks for the pointer to the URL. This http://www.classiccmp.org/dunfield/s100c/wmc/cpu2.pdf is closest to what I am considering: an S-100 Z80 board with no memory and no IO except what is necessary to control an S-100 bus motherboard.

My idea is to replace the Z80 CPU in this circuit with a 40 pin connector and ECBbus signals from the Test Prototype. The ECBbus signals http://www.hardwarebook.info/ECBbus (at least rows A and C) are nearly identical to a Z80 signals except for being buffered through 74LS245 and 74LS243 bus transceivers. Leave the rest of the circuit largely as is and let its own 74LS244 bus drivers and logic on the board drive the S-100 bus.

Is the concept even plausible? Is it reasonable or practical to implement? Has anyone here done something like this before? The Test Prototype is only clocked at 4 MHz so if I keep the braided ribbon cable between the ECBbus system and the S-100 motherboard relatively short I think it should work -- at least in theory.

I'd have to build an S-100 motherboard, get the power supplies, chassis, and a S-100 prototype board for the circuit. Those could be done in phases, tested, and integrated slowly to build up the final system.

Thoughts? Thanks!

Andrew Lynch

[Thrashbarg]

I'd say the concept is definitely plausible. As I see it any bus can be interfaced to any other bus with enough glue logic. For example there's a TCP/IP project for the VIC-20 on the Internet somewhere and the guy interfaced the VIC-20's cartridge socket to an ISA bus network card.

That's one good looking machine you've built too, and you got it up and running very quickly. Congrats.

[carlsson]

Lee Davidson's VIC-20 page with hardware projects:
http://www.themotionstore.com/leeedavison/6502/vic20/

Ruud Baltissen also has a bunch of concepts and descriptions:
http://www.baltissen.org/newhtm/hardware.htm

[lynchaj]

I'd say the concept is definitely plausible. As I see it any bus can be interfaced to any other bus with enough glue logic. For example there's a TCP/IP project for the VIC-20 on the Internet somewhere and the guy interfaced the VIC-20's cartridge socket to an ISA bus network card.

That's one good looking machine you've built too, and you got it up and running very quickly. Congrats.

Thanks for the kind words. It has been a lot of fun building Test Prototype.

I would like to do some S-100 related development / interfacing to be able to interface to some pre-built S-100 cards and peripherals. Right now I am creating all the peripheral boards for Test Prototype from scratch as there are no ECBbus peripherals available to my knowledge. It is OK since I enjoy building and testing them but it would be nice to use some of the neat old S-100 boards. There are several S-100 boards available on Ebay.

Based on what I have seen, when building S-100 systems the limiting factor appears to be availability of parts. S-100 prototype boards are fairly rare and the only source online I know of is Vector Electronics http://www.vectorelect.com/Product/Plugbord/PBSTDBUS.htm and at $50 per board, it is rather expensive for casual hobbyist prototyping. Are there other less expensive sources of S-100 parts? Especially the prototype boards and motherboards.

One of the reasons I chose ECBbus is that it is highly Z80 compatible, rows A and C are practically a clone of the Z80 bus, and the parts are relatively inexpensive. I can buy a prototype board for $4-$5 and a male 96 PIN DIN 41612 for $3-$4 and build a card for just a little more than the cost of the components and wiring. Building a passive ECB backplane is similarly easy since it is just several female 96 PIN DIN 41612 regularly spaced and connected in parallel.

I am monitoring Ebay for if/when S-100 prototype boards and motherboard become available but I suspect based on reviewing the already closed Ebay sales the prices for them are going to be quite high as well.

As a side note, maybe Vintage-Computer Forums could/would add another "genre" for homebuilt vintage computers? I know I am very interested in the subject and maybe others are as well.

Thanks again!

Andrew Lynch

[ahm]

maybe Vintage-Computer Forums could/would add another "genre" for homebuilt vintage computers?

Feel free to use "S-100" or "Other".
A descriptive subject line goes a long way.

Andy

[Terry Yager]

I have a couple of used S-100 prot boards that Erik gave me a while back. I'd be happy to contribute them to a worthy cause, just pay postage. I also have a copy of Interfacing Microcomputers to the Real World, by Murray Sargent III & Richard L. Shoemaker, ISBN # 0-201-07773-6. It contains information on converting the TRS-80 bus (which is also a near-clone of the Z80, AIUI) to STD and/or S-100. If you can't find a copy on Amazon, etc, I can arrange to lend you mine. Lemme know (pm).

--T

[lynchaj]

I have a couple of used S-100 prot boards that Erik gave me a while back. I'd be happy to contribute them to a worthy cause, just pay postage. I also have a copy of Interfacing Microcomputers to the Real World, by Murray Sargent III & Richard L. Shoemaker, ISBN # 0-201-07773-6. It contains information on converting the TRS-80 bus (which is also a near-clone of the Z80, AIUI) to STD and/or S-100. If you can't find a copy on Amazon, etc, I can arrange to lend you mine. Lemme know (pm).

--T

Terry,
Thanks for the information. I sent you a PM so we can discuss the subject further offline.

In addition, I am very interested in the book you cited. Does it contain circuit diagrams and schematics on what is necessary to convert to S-100 bus interface? I will search for a copy and order one.

I considered STD bus as well but personally, I thought the STD board size is too small for my prototyping style although the 44 pin edge connector is very good. One of the main reasons I am attracted to S-100 for kit building is that the prototype boards are much larger than the rather cramped 100x130 mm and 100x160 mm sizes I am currently using.

Thanks again for the tips!

Andrew Lynch

[Terry Yager]

I may have spoken up too soon. I've been looking, but haven't found the boards yet, although, I'm moving house this month, so I'm sure they'll turn up soon. Offer for loan of book(s) still stands though.

--T

[ziloo]

One of the reasons I chose ECBbus is that it is highly Z80 compatible, rows A and C are practically a clone of the Z80 bus, and ...

Hello Andrew,

Would you please elaborate more on the compatibility of a bus with a given CPU? I have seen designs where a Z80, Ram, and some glue logic have been placed on an extension card and inserted into an EISA slot doing I/O with a PC.

Thank you

ziloo :listen:

[lynchaj]

Hello Andrew,

Would you please elaborate more on the compatibility of a bus with a given CPU? I have seen designs where a Z80, Ram, and some glue logic have been placed on an extension card and inserted into an EISA slot doing I/O with a PC.

Thank you

ziloo :listen:

ziloo,
I cannot speak in general terms or for all CPUs and/or bus combinations but certain CPU busses do reflect the original CPU used in the design. A few examples are the S-100 bus is very nearly the 8080A and chipset bus taken to a 100 pin connector. Other examples are the ECB bus which is highly similar to the Z80 bus, VME is MC68K oriented, ISA-8 based on 8088 and chipset bus, ISA-16 and PC104 based on the 80286 and chipset, and so on. Although the busses tend to favor one particular CPU, they do generally do not prevent other CPUs from adapting to the bus with sufficient glue logic in place.

There are a few non CPU specific busses out there like nubus and PCI but they tend to be the later arrivals on the microcomputer scene. ECB bus is a European standard from Kontron since Z80's were very popular in Europe for process control and as microcontrollers.

I think the ECB bus is in some ways the European response to the more American S-100 bus standard with a lot of improvements as it came out roughly 8 years later or so. I believe the ECB bus was clearly designed with the Z80 in mind. Check out its pinout:

http://www.hardwarebook.info/ECBbus

Based on the above you could practically plug a Z80 directly into an ECBbus rows A and C and it would work as is. Of course, to be useful you'd want to add buffers and some control logic for data flow and a few extras like phi2 and additional power lines.

As for EISA, I really cannot comment on that. I do know there are Z80 ISA-8 and ISA-16 cards out there but I have no practical experience with them. If I were to implement a homebuilt computer based on a bus, I would go with the CPU first designed for that bus -- for a passive ISA-8 backplane, 8088 would be the logical choice, in my opinion.

Thanks!

Andrew Lynch

[ziloo]

Thank you for your response Andrew!

The point I was making is this: What is the criteria for choosing a certain bus
as compared to another bus? Is it logistic convenience, or there are other
parameters to take into account?

ziloo :listen:

[lynchaj]

Thank you for your response Andrew!

The point I was making is this: What is the criteria for choosing a certain bus
as compared to another bus? Is it logistic convenience, or there are other
parameters to take into account?

ziloo :listen:

OK, I think I understand your question better now. I think there are three major factors in the decision to pick a bus for a homebuilt computer bus.

1.) Ease of integration with the CPU. Some busses are going to integrate better with some CPUs just because they are designed that way. See previous response on which busses versus which CPUs. If you are determined and skilled enough you probably can make almost any CPU work with any bus to some degree. The question is how difficult is it going to be and can you leverage any of the existing works already available? If I were going to make a 6800 based homebuilt computer, I would probably pick the SWTPC SS-50 bus since it would integrate well with that CPU. Since I used a Z80, the ECB bus seemed like a logical choice. Picking a compatible CPU/Bus pair also provide lots of working schematics for ideas on circuit building since there are lots of parts documented. For the 6800 example see:

http://www.swtpc.com/mholley/index.html

2.) Availability of parts. Picking a bus has to take into account whether you can get parts for it. The homebuilt computer design is useless unless you can build it. I think this is one of the major problems with kit building for the S-100 bus now is it is so time consuming and difficult to obtain even the most basic parts like bus connectors, passive backplanes, power supplies, prototype boards, and even discrete components like 7805 SCRs. This is where ECB really shines because you can fabricate the passive backplanes out of inexpensive and readily available components from Radio Shack or Jameco (insert favorite vendor here). Making the prototype boards is trivial as well since all it requires is a prototype board preferably 160x100 mm but can be any size and a 96 pin DIN connector 41612. All of which are very common. In addition, the power supplies are cheap and available since a standard PC switching PS will work or any regulated +5 supply will do. You can add other voltages as needed. S-100, ISA-8, ISA-16, and STD-80 all rely on male edge connectors which means you have to buy your own pre-made prototype boards which can really be expensive, assuming you can find them to begin with. S-100 has some unique power supply requirements and each card has its own local regulator which complicates design and construction.

3.) Personal preference. This factor trumps all others. Some people just like certain CPUs and busses and will use them no matter what else. It is a personal decision so who is to say what is right or wrong? If you are determined to put an AMD 29K CPU on a VME bus, no one is going to stop you but you are going to do a lot of work to get there. Have a good time with that project!

Hope this helps. Best of luck with your projects and let me know if I can help in any way. Thanks!

Andrew Lynch