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Progress with new S-100 bus boards

monahan_z

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Oct 19, 2008
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San Ramon, CA
FYI, I have written up some recent progress Andrew and I have had in building new S-100 bus computer boards that may be of use in CP/M and MS-DOS systems. The can be seen here:-
http://www.s100computers.com/
(The first 3 menu items).
They are a MSX compatible VDP video board, an ISA bus to S-100 bus converter board and a multi- parallel ports S-100 board. The first two are still a work in progress.
 

NobodyIsHere

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Dec 21, 2006
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Hi

Here is a little background on the S100computers & N8VEM S-100 board development from my perspective. Hopefully John can chime in on his thoughts as well.

The S-100 to ISA bridge board (aka S-100 TestIO V2) is really a development tool we've created to help get the S-100 VGA board working -- similar to the ISA VGA board we designed a while back. The VGA chipset has a problem with the S-100 bus we haven't been able to find yet. The same chipset works on the ISA bus just fine so this is an intermediate step to get our working ISA VGA board onto the S-100 bus and narrow down the problem area. Eventually this is going to result in a native S-100 VGA board.

However, the S-100 to ISA bridge may be quite a useful tool in its own right. I certainly hope so but its a side effect not a main goal. It probably needs some additional work to make it more general purpose but is definitely showing major progress. It is based on John's initial 8 bit ISA to S-100 design which I originally was advocating as a useful board. However I now see John's point on the more broader application of the 8 <-> 16 bit ISA conversion logic. I am hopeful this new board is going to bring us closer to a general purpose S-100 to ISA bridge board.

The S-100 VGA is such an important project to accomplish that we are pulling out all the stops to get it working. There have been multiple false leads, dead-ends, and non-working prototypes. However so much of the current Linux/BSD development basically assumes a VGA that without it there will be major compatibility problems. Our major development centers on basically three boards: S-100 80386 CPU, S-100 80386 SRAM, and S-100 VGA. It is also the basis of modern x86 PCs since about 1985 (386 + RAM + VGA). Everything afterward stems from it.

The S-100 ParallelIO board is a kind of a re-imagined version of the IMSAI PIO board. Basically a simple board that's useful for everyone but still easy to build and get working. It adds LEDs for debugging purposes and a general purpose PC compatible parallel printer port. With 4 input parallel ports and 4 output parallel ports and various other control signals there is a lot you can do with this board and I think it is going to be a hit. After several complex boards it is a nice change to work on something relatively straight forward.

The S-100 VDP is kind of an S-100 off-shoot of the video and sound section of the N8VEM N8 board and/or SCG. By itself it provides video (composite and sort-of-VGA) and a sound generator. It is a fun board and could be potentially useful for many things on an S-100 system. I am hoping it can be used to bring some level of MSX hardware compatibility to the S-100 bus but it is not restricted to only a Z80 CPU or the unique MSX memory bank switching scheme.

The S-100 VDP is part of another trio of boards designed to eventually allow full MSX hardware compatibility on the S-100 bus. First is the S-100 Z80 CPU board which already exists, second is the S-100 VDP which implements the video and sound sections, and finally is the S-100 Utility board which fills out the MSX hardware compatible memory "slots" and the basic IO (parallel, serial, matrix ASCII keyboard, & cassette control functions). The S-100 Utility board can also be used (like the S-100 VDP) separately from MSX as a basic 8 bit S-100 ROM, RAM plus IO board. The alternate goal being this board could be used to "bootstrap" a minimal S-100 system using a CPU board plus the S-100 Utility board only.

Many things happening on the S-100 bus these days. Feel free to join us!

Thanks and have a nice day!

Andrew Lynch
 

monahan_z

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John-
The ISA converter is another heroic project. Do you expect CP/M86 to be able to run that mixed environment?

Rick

No reason why not Rick. MS-DOS (V4.01) does, however I see this board as more of a hardware to transplant ISA board chips etc. on to new S-100 boards. This is not as easy as it sounds, see for example my current efforts with a Cirrus Logic XVGA chip
http://www.s100computers.com/My System Pages/VGA Board/VGA Board.htm.

We will probably do a prototype run for people interested in the future but I doubt there would be a large demand for the board.

John
 

NobodyIsHere

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i've been following this S-100 work off and on, and has started piquing my interest in S-100 systems. It's interesting to see an 80386-40 in the S-100, could a 486, or maybe a 586 / 686 be adapted?

Hi
I think a 486 is probably achieveable on an S-100 board. However until the 386/RAM/VGA combo is working it is kind of a moot point. Any one of those not making it really dooms future projects. Hopefully we'll see a breakthrough on the VGA board project soon with the new S-100 to ISA bridge board.

I've been rethinking the S-100 80386 SRAM board project and had a bit of a revelation yesterday. Unfortunately it has to use SMT chips to get the density we need. It makes PCB trace routing very difficult and impractical with the FreeRouting autorouter. I had a dream about it two nights ago and now have a new way to route the board. It might just work while keeping it a 2 layer PCB. At 32MB RAM we could get some of the lower end Linux/BSD systems to work.

Thanks and have a nice day!

Andrew Lynch
 

NobodyIsHere

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Hi
Possibly. We'll see. There is a certain amount of PC compatibility on the S-100 already but it never got past the 80286/CGA stage. There were a couple of S-100boards specifically designed to maximize PC compatibility. John's got information on the subject on the S100computers.com.

The goal is to allow "sophisticated" OS like BSD or Linux (32 bit CPU ISA, 32 bit wide RAM, MMU, VGA). If games happen to come along with then so be it. The 386/RAM/VGA is the absolute minimum to run a real protected mode OS like Linux. There were pseudo-Un*x variants on 16 bit machines but anything really Un*x like (BSD, Linux) started on the 386 and later.

Thanks!

Andrew Lynch
 

k2x4b524[

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Jun 13, 2009
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Tacoma, Washington, USA. Zip code 98404
regardless, this is some impressive work, if everything with the 386/memory/vga works out, would a sb 2.0 compatible sound card be in the works? I mean it really is something, knowing such an antiquated bus can be modernized to do so much :)
 
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