Hello everyone,
I am preparing my project to recreate a discrete 80286 AT PC based loosely on the IBM 5170.
I want to design an ATX form factor and ATX PSU powered 80286 mainboard which has an integrated design
for the usual interfaces such as floppy drive, IDE, serial, parallel, LAN, SCSI etc to be included onboard.
I recently bought a NCR PC-8 rev 0 mainboard which is very similar to the 5170, it was in bad shape and
a terrible factory soldering job. Unfortunately during testing I could get the mainboard running but not stable enough.
In fact, it was only getting worse and worse while there are no faulty components at all. Finally I have to conclude
that this 4 layer PCB is simply having broken traces caused by the terrible factory soldering quality. It's simply a waste
of my time to work on this PCB which doesn't even have a schematic. So I am abandoning this European made NCR PCB
as my reference for my project. I just don't trust this mainboard to be of any help through the process I am facing.
I will desolder the ICs and slot connectors so I can use them later.
So it's back to the drawing board for me. I can now do two things, either I find another 5170 or clone 5170 mainboard
which at least is working reliably, or I go from the IBM schematics completely. Which is possible, however it may
require more revisions to get it completely right which will be a whole lot more work for me. Designing a fully
integrated mainboard is really a not of work which I hope to not have to do too many times over. Even building and
testing will be a real challenge because of timing issues which I expect to come up. I hope I will still find a better
example mainboard to test and study in more detail and keep as a reference for testing certain circuits.
Anyway, I was wondering, are there some experts here on the 5170 who have experience repairing and troubleshooting
this system? I mean, are there any members of this forum who are closely familiar with the 5170 schematics and design?
Who have seen many symptoms of malfunctions and are familiar with those from back in the day, or even from working
on these systems recently?
And who would be willing to help me if I have some questions? If you are interested in my project and would like to see
it come to life, please reply here, I would appreciate it very much. I know that there is a definate chance that there is no
interest at all in what I am doing, if so, I can understand and will make it my personal project just for myself. I will probably
not need too much help or time of yours, but it may help if you are familiar with issues I may encounter.
One of the things I will do is to strip out all DRAM logic. I will simplify the design using SRAM memory. The memory will
not include any parity checking which I believe may even free up some CPU bus time. There are several programmable
logic ICs such as:
- U72 - 28S42 PROM
- U87 PAL 16L8
- U130 PAL 16L8A
Does anyone have the programing files for these?
Probably I will not be needing U72, but I would appreciate to have it anyway.
Basically what I want to do is to build a most basic AT system which I find to work reliably and 100% stable without any issues.
Probably it is only going to need a VGA card, soundcard and drives of choice to have a complete system, nothing else.
In the future I may want to try using a 386SX or a TI 486SLC CPU to develop an even faster discrete AT system based on those.
But I can't skip this first step with the 5170 based system before I can get further.
I just want to see how far I can get in building PC recreations without actually using a chipset.
I know using a chipset will surely function but that is not really a challanging or satisfying goal to me.
The 5170 is a strange and quirky design, but I have a feeling that I am going to love to use it once it's up and running in my
recreation. And after all, it was the industry standard anyway, so that's worth it for the experience to be able to run many
different classic software on it.
How long this project will take until completion really depends on how many steps I will need to take.
If I had a reference PCB, I could try to replace certain circuits, especially testing the new SRAM and redesigned memory
decoding logic. Being able to test this and other things first on a know working system will be a real help in preparing my own design stage.
So I will still keep an eye out for finding another mainboard. That is definately not going to be cheap.
Kind regards,
Rodney
I am preparing my project to recreate a discrete 80286 AT PC based loosely on the IBM 5170.
I want to design an ATX form factor and ATX PSU powered 80286 mainboard which has an integrated design
for the usual interfaces such as floppy drive, IDE, serial, parallel, LAN, SCSI etc to be included onboard.
I recently bought a NCR PC-8 rev 0 mainboard which is very similar to the 5170, it was in bad shape and
a terrible factory soldering job. Unfortunately during testing I could get the mainboard running but not stable enough.
In fact, it was only getting worse and worse while there are no faulty components at all. Finally I have to conclude
that this 4 layer PCB is simply having broken traces caused by the terrible factory soldering quality. It's simply a waste
of my time to work on this PCB which doesn't even have a schematic. So I am abandoning this European made NCR PCB
as my reference for my project. I just don't trust this mainboard to be of any help through the process I am facing.
I will desolder the ICs and slot connectors so I can use them later.
So it's back to the drawing board for me. I can now do two things, either I find another 5170 or clone 5170 mainboard
which at least is working reliably, or I go from the IBM schematics completely. Which is possible, however it may
require more revisions to get it completely right which will be a whole lot more work for me. Designing a fully
integrated mainboard is really a not of work which I hope to not have to do too many times over. Even building and
testing will be a real challenge because of timing issues which I expect to come up. I hope I will still find a better
example mainboard to test and study in more detail and keep as a reference for testing certain circuits.
Anyway, I was wondering, are there some experts here on the 5170 who have experience repairing and troubleshooting
this system? I mean, are there any members of this forum who are closely familiar with the 5170 schematics and design?
Who have seen many symptoms of malfunctions and are familiar with those from back in the day, or even from working
on these systems recently?
And who would be willing to help me if I have some questions? If you are interested in my project and would like to see
it come to life, please reply here, I would appreciate it very much. I know that there is a definate chance that there is no
interest at all in what I am doing, if so, I can understand and will make it my personal project just for myself. I will probably
not need too much help or time of yours, but it may help if you are familiar with issues I may encounter.
One of the things I will do is to strip out all DRAM logic. I will simplify the design using SRAM memory. The memory will
not include any parity checking which I believe may even free up some CPU bus time. There are several programmable
logic ICs such as:
- U72 - 28S42 PROM
- U87 PAL 16L8
- U130 PAL 16L8A
Does anyone have the programing files for these?
Probably I will not be needing U72, but I would appreciate to have it anyway.
Basically what I want to do is to build a most basic AT system which I find to work reliably and 100% stable without any issues.
Probably it is only going to need a VGA card, soundcard and drives of choice to have a complete system, nothing else.
In the future I may want to try using a 386SX or a TI 486SLC CPU to develop an even faster discrete AT system based on those.
But I can't skip this first step with the 5170 based system before I can get further.
I just want to see how far I can get in building PC recreations without actually using a chipset.
I know using a chipset will surely function but that is not really a challanging or satisfying goal to me.
The 5170 is a strange and quirky design, but I have a feeling that I am going to love to use it once it's up and running in my
recreation. And after all, it was the industry standard anyway, so that's worth it for the experience to be able to run many
different classic software on it.
How long this project will take until completion really depends on how many steps I will need to take.
If I had a reference PCB, I could try to replace certain circuits, especially testing the new SRAM and redesigned memory
decoding logic. Being able to test this and other things first on a know working system will be a real help in preparing my own design stage.
So I will still keep an eye out for finding another mainboard. That is definately not going to be cheap.
Kind regards,
Rodney