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Sergey's XT Project - Home-made IBM PC compatible system

glitch said:
Neat project! I'm getting ready to assemble one of the N8VEM SBC-188 boards, which is of course based around the 80C188. The current BIOS will boot MS-DOS 5.0 from floppy of CF card, but it's using a serial port as the console, so I'd imagine anything that doesn't use BIOS calls for string input/output won't play very well with the board.
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I have SBC-188 board myself: http://picasaweb.google.com/skiselev/SBC188 (and I actually wrote Int 10h / Int 16h functions emulation using serial for SBC-188 BIOS). It is a very nice project. And as you mention problem with it is the limited compatibility with IBM PC. It will run programs as long as they use standard BIOS or DOS calls. Anything that talks directly to hardware won't work.
 
That's quite a neat project you got there.

If you can get your hands on one of the incomplete IBM 5161 PC/XT expansion units (without receiver/extender card and cable), that would be excellent for something like this. You will have to dissable the OSC-signal generator in either the 5161 or on your card (or make it jumper selectable), but otherwise it should work. Then you wouldn't just get the correct operation, but the macine would have much the same feel as an original IBM (if you got a model M keyboard or an XT-to-AT converter with an original IBM 83-key kb laying around of course).

I once heard that incompleete 5161's were quite easy to come by, but I haven't really gone into depth about that.
 
Do you plan to sell these? I'd definitely consider buying one if so.. It'd be cool if you made multiple motherboard cards, supporting various eras of CPU... but now I'm getting ahead of myself. xD

I once heard that incompleete 5161's were quite easy to come by, but I haven't really gone into depth about that.
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In my experience they're almost impossible to come by no matter what shape they're in or how complete they are.. >.>
 
That is so cool.

So what is the baseboard thing that all the cards are plugged into? Does it need it, or will it work in a "regular" motherboard?

What would be cool as a next step would be making a baby AT board with this, the xt-ide and the (hopefully) upcoming opl2 fm card all built in with 1-2 expansion slots for video card, floppy controller, if it's also not included on the mainboard, etc.
 
Raven said:
Do you plan to sell these? I'd definitely consider buying one if so.. It'd be cool if you made multiple motherboard cards, supporting various eras of CPU... but now I'm getting ahead of myself. xD
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No plans to sell complete boards, but once PCBs are ready I might sell them (not for profit, just to cover PCB manufacturing costs). But I guess it's too early to talk about it...
 
MV75 said:
That is so cool.

So what is the baseboard thing that all the cards are plugged into? Does it need it, or will it work in a "regular" motherboard?

What would be cool as a next step would be making a baby AT board with this, the xt-ide and the (hopefully) upcoming opl2 fm card all built in with 1-2 expansion slots for video card, floppy controller, if it's also not included on the mainboard, etc.
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It plugs into a backplane board, which is basically a bunch of ISA connectors connected in parallel with power attached to power lines. Like shown here: http://www.google.com/products/cata...og_result&ct=result&resnum=3&ved=0CG4Q8wIwAg#. I use a backplane with 7 slots, and 6 of them are used by: 1. System board, 2. VGA card, 3. Sound card, 4. XT-IDE, 5. memory extension (won't be needed in PCB version, all the memory will be on the system board). 6. Floppy disk controller (I just use an AT-era multi I/O card, with IDE disabled. These cards use 16-bit slots, but only IDE really requires that, everything else works with 8-bit slot).

The system board will not work when plugged into a real motherboard. But nothing stops one from building a Baby AT sized backplane. And I guess that some of commercially produced ISA backplanes will fit into a baby AT case nicely.
 
Cool, thanks for that info. Looks like the acrosser card might mount in an AT case. The holes look like they match, do they? I'd be very interested when it goes PCB, I just love assembling these sorts of things, I really like any excuse to fire up the soldering iron. :) Making a small suitable cube type case could work too. A matx psu with an atx-at adapter would be sweet to go.

What did you use to first program the bios chip for the motherboard? A basic PIC programmer? And I guess subsequent upgrades can be done from a floppy drive with the chip in the system? For the keyboard bios, just any old "AT" keyboard bios chip with existing image on it works? I've got a few of them already scavenged from 386/486 boards. I don't know why I kept them, but I got a bunch of them and some system bios chips too.
 
MV75 said:
Cool, thanks for that info. Looks like the acrosser card might mount in an AT case. The holes look like they match, do they? I'd be very interested when it goes PCB, I just love assembling these sorts of things, I really like any excuse to fire up the soldering iron. :) Making a small suitable cube type case could work too. A matx psu with an atx-at adapter would be sweet to go.

What did you use to first program the bios chip for the motherboard? A basic PIC programmer? And I guess subsequent upgrades can be done from a floppy drive with the chip in the system? For the keyboard bios, just any old "AT" keyboard bios chip with existing image on it works? I've got a few of them already scavenged from 386/486 boards. I don't know why I kept them, but I got a bunch of them and some system bios chips too.
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I am working on PCB design, it won't be a small board. Something like 11"x4" (28x10cm), but still it is smaller than some old ISA cards (think of original CGA or MDA). I'll post a message when the PCB design is ready.
I was planning to use Jameco #323460 for power supply, hopefully 50W will be enough for everything. Micro ATX PSU will work just great, it's possible just to cut the ATX connector and connect wires to the backplane, and connect the green (power on) wire + black (ground) wire to the power switch. In general any PSU providing +5V/+12V/-12V should work. I am not aware of any boards using -5V (-5V is not provided by newer ATX power supplies).

I am using cheap ($30) Willem programmer to program the BIOS, I don't have a BIOS flash utility yet, but it shouldn't be too complicated to write one.

Regrading keyboard controller chip - I have a few of them and tested them with the board. Generally older 8042 chips (from 286/386 motherboards) won't support PS/2 mouse (will work in AT mode only). Newer ones support both AT and PS/2 mode with mouse.
Here is what I have and how it works:
- VT82C42 - works both in AT and PS/2 mode, PS/2 mouse works.
- 8042AH with AMI version F BIOS - works in AT mode, initializes in PS/2 mode, but mouse doesn't work. Could be a software issue.
- Mutsubishi 8042 pulled from a 386 board - works in AT mode, doesn't work in PS/2 mode
- 8742 (with UV EPROM) from an Intel EISA board - doesn't work in AT mode, works in PS/2 mode, but no mouse. Again, could be a software issue.
 
Hi, i want to do some similar, can you send me diagrams, names of parts, The bios, or some similar, and
Can I Install a Hard Disk, like 1 or 4 GB?
My e-mail is: gerry_prix@hotmail.com
 
gerry said:
Hi, i want to do some similar, can you send me diagrams, names of parts, The bios, or some similar, and
Can I Install a Hard Disk, like 1 or 4 GB?
My e-mail is: gerry_prix@hotmail.com
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Gerry,

You can find diagrams, including PCB design at my web page: http://www.malinov.com/Home/sergeys-projects/sergey-s-xt
I'll compile the part list and post it there too. Meanwhile you can look at schematics. I used mostly 74ALS* parts for logic ICs (schematics shows 74LS*).
I am planing to post BIOS source code and binaries soon (need to do some cleanups). But I can send them to you by e-mail if you want.

It seems that I'll be ordering PBCs soon, would you like to get a PCB? (Not sure yet about the price)
Note that this system is work in progress, and I am not sure how well it will work for you.

Regarding hard disk - I am using my system together with XT-IDE controller, and it is possible to attach almost any IDE disk to it. There are some limitations on DOS side, I think it supports up to 8GB (4 partitions of 2GB each), you can use larger disks, but DOS will be able to access only first 8GB. I am using a compact flash card and compact flash to IDE adapter instead of the hard disk. Compact flash cards are pretty cheap now and much more reliable than a hard drive.

Thanks,
Sergey
 
Project update

Project update

Hi,

An update on my XT project. I designed and ordered PCBs, which turned to be really good quality (well... my first time ordering PCBs).
I assembled one of the boards and tested it with different components (CMOS and TTL logic, various CPU types, various extension cards, etc.)
Few other PCBs were sent to N8VEM folks and hopefully some of them will finish assembling their systems soon.

IMG_6703.jpg


I've spent last month or so improving BIOS for my system, adding things like support of multiple types of floppy drives (tested up to 1.44MB 3.5", but theoretically should support 2.88MB too...), rewriting video BIOS for CGA (I guess it was more for my own entertainment, since the board works very well with VGA adapters)

If you're interested in building such a system I still have a few PCBs and other components (V20HL CPUs, keyboard controllers) left.

Project page: http://www.malinov.com/Home/sergeys-projects/sergey-s-xt
More pictures: https://picasaweb.google.com/skiselev/SergeySXT

Best regards,
Sergey
 
Nice work Sergey!

Anyone ever looked into how much a (presumably local) company would charge in tooling and per unit for punched nickel plated or chrome back plates? I know it's much cheaper for PCI cards since they can take a mass produced solid blanks and just punch whatever squares or holes you need it in. But for opposite side ISA bends, I'm afraid to go looking!
 
eeguru said:
Nice work Sergey!

Anyone ever looked into how much a (presumably local) company would charge in tooling and per unit for punched nickel plated or chrome back plates? I know it's much cheaper for PCI cards since they can take a mass produced solid blanks and just punch whatever squares or holes you need it in. But for opposite side ISA bends, I'm afraid to go looking!
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I didn't check that, but actually I wanted to do so... Keystone Electronics (http://www.keyelco.com/products/prod45.asp?SubCategoryID=26) offers both ISA and PCI brackets. I don't think that the price for ISA will be much higher than for PCI.
 
sergey said:
I didn't check that, but actually I wanted to do so... Keystone Electronics (http://www.keyelco.com/products/prod45.asp?SubCategoryID=26) offers both ISA and PCI brackets. I don't think that the price for ISA will be much higher than for PCI.
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Wow, that is a nice find. The standard ones don't fit my project needs but as I get closer to the final board layout, I might ask for a quote from them. If the standard ones fit, they are only a few dollars a piece and ship from in-stock at Mouser, Newark, etc. Tnx for link.
 
TOTALLY AWESOME! Now if only someone had a homebrew isa backplane...Too bad the system I'd want it for is an at with serial, parallel and the turbo switch built on. Still, its an option...
 
Sergey, this is fantastic! You say this is a prototype. What are you planning on doing anything with it when it's complete? I can't even begin something like that. When a company like IBM builds a new computer, like the 5150 prototype I saw photos of, they did the same kind build. It really doesn't matter though how the connections are made, as long as YOU know what they are and how the circuit is routed.

Awesome job man! I'm not alone in my sentiment. I can't wait to see what you do with the finished product. Are you planning to case the computer? What case will you use?
 
bettablue said:
Sergey, this is fantastic! You say this is a prototype. What are you planning on doing anything with it when it's complete? I can't even begin something like that. When a company like IBM builds a new computer, like the 5150 prototype I saw photos of, they did the same kind build. It really doesn't matter though how the connections are made, as long as YOU know what they are and how the circuit is routed.

Awesome job man! I'm not alone in my sentiment. I can't wait to see what you do with the finished product. Are you planning to case the computer? What case will you use?
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Thank you :)

The board above (post #32) is actually not a prototype, it is "version 1.0". The prototype board was made with point-to-point soldering (there are a couple of pictures in my Picasa). Well, I am mostly interested in electronic design, so I didn't think about the case for my system. In general it should be possible to use just a regular XT or Baby AT case, but it would be too boring :). For now I just prefer seeing the naked boards.

Concerning future plans, I am a bit busy now with some other projects (N8 home computer, and my very own CP/M Z80-based system), but I was thinking about:
1. Releasing an updated PCB, since I am almost out of the initial batch of 15 PCBs, and there are a couple of bugs in version 1.0 I would like to fix.
2. Maybe instead of #1 (or together with it) design a CPLD-based XT board, that would reduce board size, and eliminate most 74-series chips.
3. Build an 8-bit Multi I/O board (floppy, XT-IDE, serial). Something like this: http://n8vem-sbc.pbworks.com/w/file/43601675/ISA-IO - Schematics - Color.pdf
 
Hello Sergey, congratulations for your work, it's an awesome project,sorry to contact you here, is that I would like to know if you have pcb's for sale, Xi8088, SVGA card, Olp2 card, Fdd card.Backplane and Cf-lite. Thank you!
 
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