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neazoi



Joined: 02 Sep 2009
Posts: 8

PostPosted: Wed Sep 02, 2009 7:58 pm Reply with quoteBack to top

hello all this may be a bit crazy but I would like to build my own PC XT motherboard. Is there anyone else that has done so or do you know of any kits sold in the internet?

Specs:
CPU 8088 or V20
Bus 8-bit ISA

I have build elector magazine solid state floppy and run my ms-dos from this one! but a motherboard kit or complete project (schematic, bios code, pcb pattern) would be very interesting.

Thanks

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T-R-A



Joined: 02 Oct 2004
Posts: 576
Location: Western NC

PostPosted: Wed Sep 02, 2009 8:41 pm Reply with quoteBack to top

It's not as easy as it may sound. Although there's various places you could find a schematic, producing your own PWB or hard-wiring a board (there are no kits available that I know of) would take lot's of money/time. You'd also need to program your own ROMs and locate the (now mostly obsolete) parts. I'd suggest finding something on e-bay or something in a nearby scrap pile/dumpster...
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wdegroot



Joined: 03 Feb 2006
Posts: 488
Location: pennsylvanai

PostPosted: Thu Sep 03, 2009 3:26 am Reply with quoteBack to top

was a book of schematics and diagrams
for XT kit builders
A friend may still have his non-functioning kit
I have seen some xt boards that were ALL SOCKETED
implying they were built from a kit
One or more bad joints or one or more bad chips can cause the board not to work.
as soon as you fix one thing annother bad part is causing it not to work.

A friend fixed his AT motherboard and added wires and components, but he took it to work ( Bendix aerospace) and used test equipment.
I have some refurbed PC ( not XT) boards full or added yellow wires. later the boards were just tossed and replaces as it was far simpler. with a repair tag
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neazoi



Joined: 02 Sep 2009
Posts: 8

PostPosted: Thu Sep 03, 2009 6:34 am Reply with quoteBack to top

Yes I know it would not be cheap and not easy of course. I already own an XT motherboard with a v20 cpu on it but I was thinking of prototype my own to present it in the www for the homemade enthusiasts.

I already making the elector solid state floppy drive! and I also managed to find the rom program for it and I will present it as long as I finish the construction.

I guess the best source could be some old magazines. I have seen some 70's magazines with such kits but not compatible with dos programs running on x86.

The other way is to obtain a relatively small and simple xt motherboard on ebay and them do some (lot of) reverse engineering. You need to take really good and close up photographs of the assembled motherboard. Then you need to unsolder all the pars! Then you copy the bios ROM using a standard EPROM reader/programmer. Then put the disassembled motherboard into a scanner and scan it from both sides. Then do some really good image editing to produce the pcb pattern in black and white.

It is a long and painfull procedire but what you do is you actually copy the whole motherboard Smile

I was just wondering if there is an easier way Smile

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wdegroot



Joined: 03 Feb 2006
Posts: 488
Location: pennsylvanai

PostPosted: Fri Sep 04, 2009 2:54 am Reply with quoteBack to top

when I was at electro-nuklonics, they used First ibm xt's and later clone xt mb as part of their equipment.
the guys found an ibm xt with an eprom ( not a masked, non copyable prom0 and copied it
it did not work as IBM did not use a 2764
I collected bios' and images of bioses

I know the ibm pc used a 2332 chip not a 2732 chip. ( different pinout)


There was a project in radio electronics magazine to use a motorola ( mac or atari) cpu and build it in a pc/xt case with a special " kit type" mb
the hardware, except for the special mb was xt type.
it did not run dos.
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neazoi



Joined: 02 Sep 2009
Posts: 8

PostPosted: Fri Sep 04, 2009 6:39 am Reply with quoteBack to top

I made a preliminary pare for the PC-XT construction. You can see it here:

http://www.microwave.gr/giannopk/

I intend to put all the hardware and software there for everyone to see but I need some help if you have any computer magazine's articles..

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T-R-A



Joined: 02 Oct 2004
Posts: 576
Location: Western NC

PostPosted: Fri Sep 04, 2009 7:29 am Reply with quoteBack to top

Just an FYI, but you may (or may not) be taking a risk by posting the BIOS Roms. Depending on where they came from, you could be considered infringing on copyrights. Remember, Compaq successfully developed a totally compatable clone by reverse-engineering the BIOS, not copying it...

http://oldcomputers.net/compaqi.html


Last edited by T-R-A on Fri Sep 04, 2009 7:33 am; edited 1 time in total
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neazoi



Joined: 02 Sep 2009
Posts: 8

PostPosted: Fri Sep 04, 2009 7:32 am Reply with quoteBack to top

Yes I know, I copied them by myself, from the eproms.
Thanks for the note, but I believe if we forget about copyrights for a moment then we and only then we will do a step forward. After all these are just too old..
Do you propose another way of making the ROMs available?

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T-R-A



Joined: 02 Oct 2004
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Location: Western NC

PostPosted: Fri Sep 04, 2009 7:35 am Reply with quoteBack to top

Legally, it would only be possible if someone already owned a set (and then I wouldn't be 100% sure)...
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neazoi



Joined: 02 Sep 2009
Posts: 8

PostPosted: Fri Sep 04, 2009 7:42 am Reply with quoteBack to top

Ok now we are a bit out of topic, but is it better to ask the users to email me to give them the rom and not make them available in the site? (bad form.. but..)

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neazoi



Joined: 02 Sep 2009
Posts: 8

PostPosted: Fri Sep 04, 2009 8:14 am Reply with quoteBack to top

Ok I added a copyright notice, nothing special but better than nothing..

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wdegroot



Joined: 03 Feb 2006
Posts: 488
Location: pennsylvanai

PostPosted: Fri Sep 04, 2009 4:16 pm Reply with quoteBack to top

what if someone had a motherboard or an original bios and sent that?
I do not think sending an original bios would violate
any copyright laws,. I know that back in the 1980's they sold original " upgrade" bioses for xt's.
and somewhere I found a batch of award AT 286 chjipsd

as far as a "sim,ple xt mb" I think that all pretty much followed the original IBM layout
a few like the Juko may have been different.
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IBM Portable PC



Joined: 23 Dec 2007
Posts: 60
Location: Melbourne, Australia

PostPosted: Sun Sep 06, 2009 11:59 am Reply with quoteBack to top

neazoi wrote:

I have build elector magazine solid state floppy and run my ms-dos from this one!


What edition of Elektor was this in?
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neazoi



Joined: 02 Sep 2009
Posts: 8

PostPosted: Thu Dec 17, 2009 8:38 am Reply with quoteBack to top

I do not know what was the issue in English as I have it from the Greek Elector version which dated back to 1994. I have build some more stiff on http://www.microwave.gr/giannopk/computer.htm for you to see

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wdegroot



Joined: 03 Feb 2006
Posts: 488
Location: pennsylvanai

PostPosted: Thu Dec 17, 2009 4:32 pm Reply with quoteBack to top

I think. even way back in the 1980's most of the xt clones were multi-layer pc boards
. they could have as many as 5 layers.
and the wirinbg and hookup of the board was complicated.
I think the only way you could find a kit was to locate someone who originally purchased one, then put it away and forgot about it.
contacting such a person may be difficult.

I assembled a 20 year old heathkit and had to toss out age-blackened parts like sockets or scrape and re-tin them. All the rubber grommets had beconme like stones, and the vinyl wire had become sticky.

Some old sockets may have beconme corroded and not work.
Using new parts back in the 1970's I assembeled at wpork, a microprocessor controller.
I did it with great care. it did not work. the engineer a real whiz pointed out one socket and I repleaced it and then the entire circuit worked properly.

everyone I talked to was unsucessful in making
one of these kits work
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