Venture wrote on 2023-11-02, 16:30:

Recently, I turned the machine and was greeted by some bleeps and a load of rubbish on the PC monitor

I trust you pulled phone out of your pocked and made a picture, right? right? 😀

Venture wrote on 2023-11-02, 16:30:

Whilst all this was happening, I was searching for a replacement SBC and I found an identical one from a guy in Holland. When this board arrived it behaved exactly the same as my failed one - one long beep followed by 3 short beeps and no boot.

Venture wrote on 2023-11-02, 16:30:

So, in a nutshell I have two broken SBCs. One beeps and the other does nothing.

so do they behave exactly the same or not?
That other ram you tested with, does it work in 486 fine?
$10 POST code ISA card from Amazon will tell you more

rasl_pl

Thanks for the reply. Sure, I can make a video of the bleeps and also a picture of the LCD rubbish. Will post that shortly.

1. No, the motherboards don't behave the same. First they did, then I tried the Necroware RTC board and it's made one motherboard totally dead. The replacement one I got still does the beeps.
2. Yes, all the RAM sticks tested in the 486 board fine.
3. I saw this card on Post card Necroware's Youtube videos, not sure what it is or does - I can get one no problem but will need help reading the results. Also, my PC is a backplane style which the SBC plugs into, so not sure the best place to plugs the post card in to. Can you provide a link to buy this card please? I had a quick look on Ebay and there are lots of models, it'd be good to know a recommended one.

Lastly, I got impatient and ordered some replacement onboard RAM chips (new) from Ebay. The original are CY7C199-12VC and I got replacements of CY7c199-20VC. The difference is between 12ns and 20ns access time. I am hoping this won't make a huge difference. In any case I can replace the old RAM ICs if needed.

As promised, here is a link for a video of the "better" motherboard. As far as I can tell, it's on long beep followed by 3 beeps. It also seems to repeat twice quickly so a little confusing to listen to.

https://vimeo.com/880962425?share=copy

Also attached are photos of the spare connectors available on the backplane board. Hopefully a Post card can fit?

Venture wrote on 2023-11-03, 12:30:

Thanks for the reply. Sure, I can make a video of the bleeps and also a picture of the LCD rubbish.

bleeps are bleeps so no need for video, but the picture might say something
EDIT: I was wrong, bleeps are not just bleeps, your bleeps were weird 😀
1 Long Beep + 2 Short Beeps combined with 1 Long Beep + 3 Short Beeps?
bad VIDEO ram
https://vimeo.com/880962425 shows SBC booting just fine. Video card is bad? Are you using ISA card plugged into backplane? Try another one.

I wrote below text before watching your video. Forget about it for a minute, lets concentrate on corrupted video. Start by unplugging Everything from bacplane, and plugging only graphic card back.

Venture wrote on 2023-11-03, 12:30:

1. No, the motherboards don't behave the same. First they did, then I tried the Necroware RTC board and it's made one motherboard totally dead. The replacement one I got still does the beeps.

fish old RTC chip out from garbage and follow those tutorials
https://imgur.com/gallery/N5GEx
https://www.ardent-tool.com/misc/Dallas_Rework.html
http://users.glitchwrks.com/~glitch/2017/07/2 … /ds1387-rebuild

Venture wrote on 2023-11-03, 12:30:

3. I saw this card on Post card Necroware's Youtube videos, not sure what it is or does - I can get one no problem but will need help reading the results.

thats the idea, board has standard amibios so post codes will reveal where the problem starts

Venture wrote on 2023-11-03, 12:30:

Also, my PC is a backplane style which the SBC plugs into, so not sure the best place to plugs the post card in to.

Same place other cards plug into, the backplane.
Do you have another backup backplane? If both SBC cards fail in same way it would be prudent to eliminate all common factors. That means anoter ower supply, another backplane, another ram, another video card (if its separate), etc

Venture wrote on 2023-11-03, 12:30:

Can you provide a link to buy this card please? I had a quick look on Ebay and there are lots of models, it'd be good to know a recommended one.

what country are you in? if anything with Amazon delivery this should arrive fast https://www.amazon.com/Diagnostic-Measuring-C … /dp/B08QRCDR9D/ if not look on ebay for a card that looks exactly like this one (two GAL chips), they are usually ~$6 on ebay with free shipping.

Venture wrote on 2023-11-03, 12:30:

Lastly, I got impatient and ordered some replacement onboard RAM chips (new) from Ebay. The original are CY7C199-12VC and I got replacements of CY7c199-20VC. The difference is between 12ns and 20ns access time. I am hoping this won't make a huge difference. In any case I can replace the old RAM ICs if needed.

you dont know what is broken and your first instinct is to desolder and solder more stuff, not good 😀

rasz_pl wrote on 2023-11-03, 18:59:

bleeps are bleeps so no need for video, but the picture might say something EDIT: I was wrong, bleeps are not just bleeps, your […]
Show full quote

bleeps are bleeps so no need for video, but the picture might say something
EDIT: I was wrong, bleeps are not just bleeps, your bleeps were weird 😀
1 Long Beep + 2 Short Beeps combined with 1 Long Beep + 3 Short Beeps?
bad VIDEO ram
https://vimeo.com/880962425 shows SBC booting just fine. Video card is bad? Are you using ISA card plugged into backplane? Try another one.

I wrote below text before watching your video. Forget about it for a minute, lets concentrate on corrupted video. Start by unplugging Everything from bacplane, and plugging only graphic card back.

Ok, removed all cards apart from SBC & Graphics. Beeps still the same, apart from two short beeps at the end similar to when the PC used to boot normally are missing.

Put the cards back in and tried removing graphics, this time beeps are totally different, but I can't see anything on the monitor of course. It's a lot of short beeps followed by two normal beeps. Sounds like it's saying "no graphics card installed" Video here- https://vimeo.com/881018330?share=copy

You could be right about the graphics card, but the good 486 SBC works fine with two graphics cards I have. Could it really be that two graphics cards have failed in the same way, causing only the Pentium 586 SBCs to misbehave??

Actually, the graphics card is somewhat special in that it's a "machine vision card" used in industrial applications, as well as having VGA outputs it can capture images from two CCTV cameras.

Maybe a good step would be to get a simple old VGA card from somewhere?

rasz_pl wrote on 2023-11-03, 18:59:

fish old RTC chip out from garbage and follow those tutorials https://imgur.com/gallery/N5GEx https://www.ardent-tool.com/misc/D […]
Show full quote

fish old RTC chip out from garbage and follow those tutorials
https://imgur.com/gallery/N5GEx
https://www.ardent-tool.com/misc/Dallas_Rework.html
http://users.glitchwrks.com/~glitch/2017/07/2 … /ds1387-rebuild

Yes, I will do this but I have tried SBC with known good RTC and it is the same.

rasz_pl wrote on 2023-11-03, 18:59:

Do you have another backup backplane? If both SBC cards fail in same way it would be prudent to eliminate all common factors. That means another power supply, another backplane, another ram, another video card (if its separate), etc

Yes, I have two of everything. I have one known good 486 SBC and it works in both backplanes with working graphics & all peripherals. Machines only stop working when I plug in either of the Pentium SBCs.

rasz_pl wrote on 2023-11-03, 18:59:

what country are you in? if anything with Amazon delivery this should arrive fast https://www.amazon.com/Diagnostic-Measuring-C … /dp/B08QRCDR9D/ if not look on ebay for a card that looks exactly like this one (two GAL chips), they are usually ~$6 on ebay with free shipping.

I'm in the UK. I will get one of these post cards ASAP.

rasz_pl wrote on 2023-11-03, 18:59:

you dont know what is broken and your first instinct is to desolder and solder more stuff, not good 😀

You're quite right, that was a bad idea. I was getting a little annoyed by the whole situation. 😀 For your reference / amusement, I replaced all the 12ns RAM chips with brand new 20ns RAM chips. It made the bleeping go away but the SBC did nothing so I temporarily made it worse. You'll be happy to know I replaced all the original RAM chips and we are back to the bleeping again. That was 2 hours of my life I'll never get back!!

Venture wrote on 2023-11-03, 20:29:

Ok, removed all cards apart from SBC & Graphics. Beeps still the same, apart from two short beeps at the end similar to when the PC used to boot normally are missing.

try graphic card in another slot

Venture wrote on 2023-11-03, 20:29:

Put the cards back in and tried removing graphics, this time beeps are totally different, but I can't see anything on the monitor of course. It's a lot of short beeps followed by two normal beeps. Sounds like it's saying "no graphics card installed" Video here- https://vimeo.com/881018330

'1 Long Beep + 8 Short Beeps' for no graphic card, followed by memory test and '2 short beeps' still signaling Memory test error? hard to tell with graphic card not working. https://www.lifewire.com/amibios-beep-codes-2624543

Venture wrote on 2023-11-03, 20:29:

You could be right about the graphics card, but the good 486 SBC works fine with two graphics cards I have. Could it really be that two graphics cards have failed in the same way, causing only the Pentium 586 SBCs to misbehave??

so you remove Pentium SBC, put 486 SBC in same slot and graphics magically work and PC boots correctly? This is indeed weird, only hypothetical cause I can come up with right now for something like this would be: graphic card/backplane somehow failing to work in full 16bit mode, Pentium requiring full 16bit ISA, 486 tolerating 8bit?

Venture wrote on 2023-11-03, 20:29:

Actually, the graphics card is somewhat special in that it's a "machine vision card" used in industrial applications, as well as having VGA outputs it can capture images from two CCTV cameras.

post photo of this video card please

Venture wrote on 2023-11-03, 20:29:

Maybe a good step would be to get a simple old VGA card from somewhere?

Definitely try another ordinary ISA graphic card, you can also try PCI VGA since Pentium SBC supports PCI bus.

Venture wrote on 2023-11-03, 20:29:

Yes, I will do this but I have tried SBC with known good RTC and it is the same.

Yeah, its very unlikely at this point that the problem was in RTC, unless there is some special BIOS setting required to make the ISA card work correctly and empty battery erased CMOS settings? But how would one get to that bios setting in the first place? and that wouldnt explain two motherboards doing same thing, did you mess with RTC of the second SBC right after receiving it and before trying it out? Maybe SBC clocks ISA bus too fast out of the box? Maybe it will boot with this special ISA graphic card and ordinary PC PCI VGA simultaneously? Maybe CMOS SRAM contains some secret magic key required to properly initialize this proprietary special graphic card? Did your 486 SBC come from same machine originally? Can this be some secret sauce cloning protection/software license key thing?
You could try backing up CMOS ram in 486 board, unplugging RTC chip on live system, plugging one of your spare modules in, loading settings back in, swapping it back to Pentium system and trying to boot that.

Venture wrote on 2023-11-03, 20:29:

Yes, I have two of everything. I have one known good 486 SBC and it works in both backplanes with working graphics & all peripherals. Machines only stop working
when I plug in either of the Pentium SBCs.

Your 486 box has second special graphic card or are you reusing the same one?

Venture wrote on 2023-11-03, 20:29:

I'm in the UK. I will get one of these post cards ASAP.

I think it will just say Graphic card init fail like the beeps, but its cheap enough to be worth having anyway

Venture wrote on 2023-11-03, 20:29:

You're quite right, that was a bad idea. I was getting a little annoyed by the whole situation. 😀 For your reference / amusement, I replaced all the 12ns RAM chips with brand new 20ns RAM chips. It made the bleeping go away but the SBC did nothing so I temporarily made it worse. You'll be happy to know I replaced all the original RAM chips and we are back to the bleeping again. That was 2 hours of my life I'll never get back!!

CY7C199 is SRAM so that should be cache. I dont know why there are 6 chips, weird number for cache. Replacing 12ns cache SRAM with 20ns definitely has potential to stop the board from booting completely, except if it was Cache bios should still have chance to beep error codes. The one ebay $4500 listing for that SBC has all 8 soldered in, picture quality is terrible, but it almost looks like -15 version chips.

rasz_pl wrote on 2023-11-04, 00:46:

try graphic card in another slot

Done. Still the same.

rasz_pl wrote on 2023-11-04, 00:46:

so you remove Pentium SBC, put 486 SBC in same slot and graphics magically work and PC boots correctly?

Yes, I have two machines with same graphics cards. 486 board works in both of them. Original and replacement Pentium SBCs don't work in either of them.

rasz_pl wrote on 2023-11-04, 00:46:

This is indeed weird, only hypothetical cause I can come up with right now for something like this would be: graphic card/backplane somehow failing to work in full 16bit mode, Pentium requiring full 16bit ISA, 486 tolerating 8bit?

Maybe, I'm not sure. Only way to tell is get another, more simple grahpics card. Attached is picture of current graphics card. For reference, it's Scorpion machine vision card (that's all I know). The top VGA connector is used for the monitor, the middle VGA connector is for two camera inputs (I think) and the bottom BNC connector is used for another camera where you can overlay video on to the PC screen, so it basically mixes the camera input which graphics output.

rasz_pl wrote on 2023-11-04, 00:46:

Definitely try another ordinary ISA graphic card, you can also try PCI VGA since Pentium SBC supports PCI bus.

I will just have a look on Ebay UK but I'm not really sure what to look for. I'll check it out and maybe post some links later? Not sure if I select a random old graphics card on Ebay it might be too new & not work.

rasz_pl wrote on 2023-11-04, 00:46:

Yeah, its very unlikely at this point that the problem was in RTC, unless there is some special BIOS setting required to make the ISA card work correctly and empty battery erased CMOS settings? But how would one get to that bios setting in the first place? and that wouldnt explain two motherboards doing same thing, did you mess with RTC of the second SBC right after receiving it and before trying it out?

No, I did not remove RTC from replacement Pentium SBC before trying it, it was DOA. I know that if I leave the RTC unplugged from the SBC, it does nothing, no beeps just dead. To me., this indicates that even with failing RTC it is probably trying to boot.
What backs this theory up a little is that if I put in an old RTC into the 486 board it give a "CMOS battery low" message at boot but you can still get in to BIOS etc etc.

rasz_pl wrote on 2023-11-04, 00:46:

Maybe SBC clocks ISA bus too fast out of the box? Maybe it will boot with this special ISA graphic card and ordinary PC PCI VGA simultaneously?

Not sure about this. Maybe. Only way to tell is try another graphics card I guess.

rasz_pl wrote on 2023-11-04, 00:46:

Maybe CMOS SRAM contains some secret magic key required to properly initialize this proprietary special graphic card?

Could be, but I don't think so. The reason is that the 486 SBC needs settings changed in the BIOS to work for this grapghics card, not for the VGA output but for the "frame grabber" functions. I know this, because when removing known good RTC module from working 486 board the BIOS forgot all the settings and I had to change them back. Even with the graphics card not working properly, you can still see VGA output, get can then get into the BIOS and make the changes which allow the "frame grabber" function to work. I was told by an technician who used to work on these machines, that the BIOS changes you need to make are this:

BIOS “Advanced Setup” you need to have:

Adaptor Shadow Cacheable DISABLED
System BIOS Shadow Cacheable DISABLED
ISA Video ROM C000,32K ABSENT

In Chipset Setup :

VGA farme buffer size DISABLED
All IRQ’s set to ISA
VGA Pallette Snoop DISABLED

I had no idea what any of the above means, but I found similar things in the BIOS of the 486 board, changed them and it started working again. Note; I only had to make those changes because I pulled out the known working RTC module from the 486 board to try it in the faulty Pentium SBCs.

rasz_pl wrote on 2023-11-04, 00:46:

Did your 486 SBC come from same machine originally? Can this be some secret sauce cloning protection/software license key thing?

The 486 board came from a spare PC which I bought and now using as a test bed. It has all the same cards as my machine. PCs are identical. I don't think any security stuff is installed on it, the reason being that the software was written for this machine and the application is so niche. Basically you need one of these machines for the software to be any use. It's all running on DOS, not Windows. We are talking 1993 / 1994 vintage.

rasz_pl wrote on 2023-11-04, 00:46:

You could try backing up CMOS ram in 486 board, unplugging RTC chip on live system, plugging one of your spare modules in, loading settings back in, swapping it back to Pentium system and trying to boot that.

Not sure how to do that! I am a little hesitant to mess with the working 486 card again too much, since my machine currently depends on it. After all, by simply unplugging the good RTC from there I was able to make it forget the correct grahpics card settings for the video inputs. My preferred route would be to try and diagnose & fix these two Pentium boards if I can, whilst leaving the working machine alone.

rasz_pl wrote on 2023-11-04, 00:46:

Your 486 box has second special graphic card or are you reusing the same one?

I have two graphics cards both the same. One is in working machine, other installed in space PC.

Venture wrote on 2023-11-03, 20:29:

I'm in the UK. I will get one of these post cards ASAP.

rasz_pl wrote on 2023-11-04, 00:46:

I think it will just say Graphic card init fail like the beeps, but its cheap enough to be worth having anyway

I had a look around for the Post card and Amazon can deliver late next week. Ebay is the same so it'll be a few days before we can test.

rasz_pl wrote on 2023-11-04, 00:46:

CY7C199 is SRAM so that should be cache. I dont know why there are 6 chips, weird number for cache. Replacing 12ns cache SRAM with 20ns definitely has potential to stop the board from booting completely, except if it was Cache bios should still have chance to beep error codes. The one ebay $4500 listing for that SBC has all 8 soldered in, picture quality is terrible, but it almost looks like -15 version chips.

You're right. Originally the board has 8 RAM chips on it. When I took the photo I had already desoldered two! Initially my idea was to desolder one at a time, swapping it for one on the other Pentium board just in case one faulty RAM IC was bringing the whole SBC down. I quickly got bored of that idea and went for the option of buying the slower RAM chips on Ebay and installing them, also a shitty idea. For reference, the board behaved the same with 8 RAM chips, 6 RAM chips or zero RAM chips, I tried a few different things! 😀
If you found the Ebay listing then you must've fallen off your chair like I did. How crazy is it that someone can try to charge $4500 for a "maybe working" board with zero warranty, I think that's outrageous. I know there maybe someone in the world who needs a machine in a factory somewhere to get working again ASAP but it's a huge risk to take, especially as the SBCs used in there are somewhat generic.

Graphics cards-

https://www.ebay.co.uk/itm/204528015158

https://www.ebay.co.uk/itm/225846157640

https://www.ebay.co.uk/itm/325803409109

https://www.ebay.co.uk/itm/285527971949

https://www.ebay.co.uk/itm/325617604930

There are lots more but the connector layout seems wrong / backwards to my backplane.
Thanks!

Venture wrote on 2023-11-04, 16:56:

Done. Still the same. […]
Show full quote

rasz_pl wrote on 2023-11-04, 00:46:

try graphic card in another slot

Done. Still the same.

rasz_pl wrote on 2023-11-04, 00:46:

so you remove Pentium SBC, put 486 SBC in same slot and graphics magically work and PC boots correctly?

Yes, I have two machines with same graphics cards. 486 board works in both of them. Original and replacement Pentium SBCs don't work in either of them.

rasz_pl wrote on 2023-11-04, 00:46:

This is indeed weird, only hypothetical cause I can come up with right now for something like this would be: graphic card/backplane somehow failing to work in full 16bit mode, Pentium requiring full 16bit ISA, 486 tolerating 8bit?

Maybe, I'm not sure. Only way to tell is get another, more simple grahpics card. Attached is picture of current graphics card. For reference, it's Scorpion machine vision card (that's all I know). The top VGA connector is used for the monitor, the middle VGA connector is for two camera inputs (I think) and the bottom BNC connector is used for another camera where you can overlay video on to the PC screen, so it basically mixes the camera input which graphics output.

rasz_pl wrote on 2023-11-04, 00:46:

Definitely try another ordinary ISA graphic card, you can also try PCI VGA since Pentium SBC supports PCI bus.

I will just have a look on Ebay UK but I'm not really sure what to look for. I'll check it out and maybe post some links later? Not sure if I select a random old graphics card on Ebay it might be too new & not work.

rasz_pl wrote on 2023-11-04, 00:46:

Yeah, its very unlikely at this point that the problem was in RTC, unless there is some special BIOS setting required to make the ISA card work correctly and empty battery erased CMOS settings? But how would one get to that bios setting in the first place? and that wouldnt explain two motherboards doing same thing, did you mess with RTC of the second SBC right after receiving it and before trying it out?

No, I did not remove RTC from replacement Pentium SBC before trying it, it was DOA. I know that if I leave the RTC unplugged from the SBC, it does nothing, no beeps just dead. To me., this indicates that even with failing RTC it is probably trying to boot.
What backs this theory up a little is that if I put in an old RTC into the 486 board it give a "CMOS battery low" message at boot but you can still get in to BIOS etc etc.

rasz_pl wrote on 2023-11-04, 00:46:

Maybe SBC clocks ISA bus too fast out of the box? Maybe it will boot with this special ISA graphic card and ordinary PC PCI VGA simultaneously?

Not sure about this. Maybe. Only way to tell is try another graphics card I guess.

rasz_pl wrote on 2023-11-04, 00:46:

Maybe CMOS SRAM contains some secret magic key required to properly initialize this proprietary special graphic card?

Could be, but I don't think so. The reason is that the 486 SBC needs settings changed in the BIOS to work for this grapghics card, not for the VGA output but for the "frame grabber" functions. I know this, because when removing known good RTC module from working 486 board the BIOS forgot all the settings and I had to change them back. Even with the graphics card not working properly, you can still see VGA output, get can then get into the BIOS and make the changes which allow the "frame grabber" function to work. I was told by an technician who used to work on these machines, that the BIOS changes you need to make are this:

BIOS “Advanced Setup” you need to have:

Adaptor Shadow Cacheable DISABLED
System BIOS Shadow Cacheable DISABLED
ISA Video ROM C000,32K ABSENT

In Chipset Setup :

VGA farme buffer size DISABLED
All IRQ’s set to ISA
VGA Pallette Snoop DISABLED

I had no idea what any of the above means, but I found similar things in the BIOS of the 486 board, changed them and it started working again. Note; I only had to make those changes because I pulled out the known working RTC module from the 486 board to try it in the faulty Pentium SBCs.

rasz_pl wrote on 2023-11-04, 00:46:

Did your 486 SBC come from same machine originally? Can this be some secret sauce cloning protection/software license key thing?

The 486 board came from a spare PC which I bought and now using as a test bed. It has all the same cards as my machine. PCs are identical. I don't think any security stuff is installed on it, the reason being that the software was written for this machine and the application is so niche. Basically you need one of these machines for the software to be any use. It's all running on DOS, not Windows. We are talking 1993 / 1994 vintage.

rasz_pl wrote on 2023-11-04, 00:46:

You could try backing up CMOS ram in 486 board, unplugging RTC chip on live system, plugging one of your spare modules in, loading settings back in, swapping it back to Pentium system and trying to boot that.

Not sure how to do that! I am a little hesitant to mess with the working 486 card again too much, since my machine currently depends on it. After all, by simply unplugging the good RTC from there I was able to make it forget the correct grahpics card settings for the video inputs. My preferred route would be to try and diagnose & fix these two Pentium boards if I can, whilst leaving the working machine alone.

rasz_pl wrote on 2023-11-04, 00:46:

Your 486 box has second special graphic card or are you reusing the same one?

I have two graphics cards both the same. One is in working machine, other installed in space PC.

Venture wrote on 2023-11-03, 20:29:

I'm in the UK. I will get one of these post cards ASAP.

rasz_pl wrote on 2023-11-04, 00:46:

I think it will just say Graphic card init fail like the beeps, but its cheap enough to be worth having anyway

I had a look around for the Post card and Amazon can deliver late next week. Ebay is the same so it'll be a few days before we can test.

rasz_pl wrote on 2023-11-04, 00:46:

CY7C199 is SRAM so that should be cache. I dont know why there are 6 chips, weird number for cache. Replacing 12ns cache SRAM with 20ns definitely has potential to stop the board from booting completely, except if it was Cache bios should still have chance to beep error codes. The one ebay $4500 listing for that SBC has all 8 soldered in, picture quality is terrible, but it almost looks like -15 version chips.

You're right. Originally the board has 8 RAM chips on it. When I took the photo I had already desoldered two! Initially my idea was to desolder one at a time, swapping it for one on the other Pentium board just in case one faulty RAM IC was bringing the whole SBC down. I quickly got bored of that idea and went for the option of buying the slower RAM chips on Ebay and installing them, also a shitty idea. For reference, the board behaved the same with 8 RAM chips, 6 RAM chips or zero RAM chips, I tried a few different things! 😀
If you found the Ebay listing then you must've fallen off your chair like I did. How crazy is it that someone can try to charge $4500 for a "maybe working" board with zero warranty, I think that's outrageous. I know there maybe someone in the world who needs a machine in a factory somewhere to get working again ASAP but it's a huge risk to take, especially as the SBCs used in there are somewhat generic.

This video card with dual video outputs, is not suitable for this and loads of PAL ICs from my experience are known issues as they age, they die. PAL is programmable logic that you burn once to PAL ICs.

Get regular video card, I really like WD chipset the best for compatibility and speed. WDC90C11 make sure is 512K, or WDC90C30 or WDC90C31, both 1MB.
Another option is use PCI video card, Cirrus logic GD5430 2MB or 5446 2MB is excellent choice, Trio 64V+ 2MB is another excellent choice.

This comes from experience using a early bios that can initialize these video card properly. There is bios incompatibles with too new video cards too, all you get is no image or bleeps.

Cheers,

Venture wrote on 2023-11-04, 16:56:

Yes, I have two machines with same graphics cards. 486 board works in both of them. Original and replacement Pentium SBCs don't work in either of them.

Do you have access to normal old PC with ISA bus? would be interesting trying your special vision cards in normal PC
BIOS options you listed arent anything special, just disabled caching.

Venture wrote on 2023-11-04, 16:56:

Attached is picture of current graphics card. For reference, it's Scorpion machine vision card (that's all I know). The top VGA connector is used for the monitor, the middle VGA connector is for two camera inputs (I think) and the bottom BNC connector is used for another camera where you can overlay video on to the PC screen, so it basically mixes the camera input which graphics output.

resolution too low to read CHIPS chip markings, is it something like F82C451?

Venture wrote on 2023-11-04, 16:56:

I will just have a look on Ebay UK but I'm not really sure what to look for. I'll check it out and maybe post some links later? Not sure if I select a random old graphics card on Ebay it might be too new & not work.

ISA is ISA, PCI is PCI, anything pre ~1997 should work.

Venture wrote on 2023-11-04, 16:56:

Could be, but I don't think so. The reason is that the 486 SBC needs settings changed in the BIOS to work for this grapghics card, not for the VGA output but for the "frame grabber" functions. I know this, because when removing known good RTC module from working 486 board the BIOS forgot all the settings and I had to change them back. Even with the graphics card not working properly, you can still see VGA output

yeah, that kills secret SRAM key theory

Venture wrote on 2023-11-04, 16:56:

I have two graphics cards both the same. One is in working machine, other installed in space PC.

and both give same picture/beeps in both backplanes with two different power supplies, and with different RAM, and two separate SBCs? 😒
both have same jumper settings?
Reseating all socketed chips never hurts.

Venture wrote on 2023-11-04, 16:56:

You're right. Originally the board has 8 RAM chips on it. When I took the photo I had already desoldered two! Initially my idea was to desolder one at a time, swapping it for one on the other Pentium board just in case one faulty RAM IC was bringing the whole SBC down. I quickly got bored of that idea and went for the option of buying the slower RAM chips on Ebay and installing them, also a shitty idea. For reference, the board behaved the same with 8 RAM chips, 6 RAM chips or zero RAM chips, I tried a few different things! 😀

So its definitely cache 😀 Cache initialization is later in boot sequence, 2 missing chips will result in BIOS not detecting any and leaving disabled cache.

Venture wrote on 2023-11-04, 16:56:

If you found the Ebay listing then you must've fallen off your chair like I did. How crazy is it that someone can try to charge $4500 for a "maybe working" board with zero warranty, I think that's outrageous. I know there maybe someone in the world who needs a machine in a factory somewhere to get working again ASAP but it's a huge risk to take, especially as the SBCs used in there are somewhat generic.

😀 $4K is nothing when your >$100K a day production line is stopped.

All the cards you linked are fine, get one ISA and one PCI just in case. Alternatively look for hackerspaces near you instead of buying more and more useless hardware. There is always at least one guy in a hackerspace with vintage hardware hoard happy to help revive weird PC.

Battle plan now is to power Pentium SBC with only ordinary VGA card plugged in, get proper video, set BIOS to slowest/everything disabled, swap VGA for Vision card and hope for the best.
My best theory right now is ISA clock? Do you have a scope? Measure ISA pin B20 (CLK) in working 486 setup, and then again with Pentium SBC. There is a slight chance Pentium board starts with most conservative ISA divider (4-7MHz) letting video BIOS initialize, but then switching to higher clock (8MHz) resulting in garbage on screen.

First 4 ebay links are not good. Slow or too limited or incompatiable.
The last link is Trio64V+ which is best choice for yours.

My recommendations still stands. Keep in mind you have no choice on good compatible video cards and some video card is spendy but totally worth it.
I ran into motherboard incompatibility too with too new video cards like Riva 128, TNT2 64 PCI etc and the board was early motherboard even it was a HX chipset but too early version.
Yours is too early version and these listed video card that I recommended to you will work totally well.

Cheers,

pentiumspeed wrote on 2023-11-04, 22:19:

First 4 ebay links are not good. Slow or too limited or incompatiable.

We arent building ultimate DOS gaming machine here 😐 There is nothing incompatible in any of listed cards.

Trident 9000i very slow, Realtek slow and not compatible.

Trident 8900D with 1MB is generally good compatible with DOS, and Trio64V+ very compatible and speedy, both are also compatible with early motherboard like yours. His is pentium 66.

Another choice like WD chip I suggested are bit faster than trident.

Cheers,

pentiumspeed wrote on 2023-11-04, 22:44:

Trident 9000i very slow, Realtek slow and not compatible.

Are they too slow to boot into BIOS?

Slow during gaming and using it in windows too.

Very noticeable, trust me.

Cheers,

pentiumspeed is everything all right with you?

rasz_pl wrote on 2023-11-04, 21:22:

Do you have access to normal old PC with ISA bus? would be interesting trying your special vision cards in normal PC

Unfortunately not, just these two backplane PCs.

rasz_pl wrote on 2023-11-04, 21:22:

ISA is ISA, PCI is PCI, anything pre ~1997 should work.

Since a couple of you are having a discussion about suitable graphics card(s) for this machine, are all the Ebay links I posted suitable? It'd be good to get some clarity on this if possible.

rasz_pl wrote on 2023-11-04, 21:22:

Reseating all socketed chips never hurts.

OK, understood. Seeing that these graphics cards are both behaving the same and they are rare, and there are a LOT of socketed ICs on there, I think I will leave this till later and go with other diagnosis first.

rasz_pl wrote on 2023-11-04, 21:22:

All the cards you linked are fine, get one ISA and one PCI just in case. Alternatively look for hackerspaces near you instead of buying more and more useless hardware. There is always at least one guy in a hackerspace with vintage hardware hoard happy to help revive weird PC.

Good idea. I'm in London, UK and will need to look in to this. Any members in the UK know a good hackerspace with a PC guy?

rasz_pl wrote on 2023-11-04, 21:22:

Battle plan now is to power Pentium SBC with only ordinary VGA card plugged in, get proper video, set BIOS to slowest/everything disabled, swap VGA for Vision card and hope for the best.

I like this theory. Reason is that it doesn't make sense to me that two Pentium machines of roughly the same age fail in exactly the same way. My experience tells me that it's not likely to be an IC but something like an RTC battery. Maybe this Pentium SBC doesn't like the graphics card out of the box but the 486 will at least work to give a VGA output.

rasz_pl wrote on 2023-11-04, 21:22:

My best theory right now is ISA clock? Do you have a scope? Measure ISA pin B20 (CLK) in working 486 setup, and then again with Pentium SBC. There is a slight chance Pentium board starts with most conservative ISA divider (4-7MHz) letting video BIOS initialize, but then switching to higher clock (8MHz) resulting in garbage on screen.

Sure, I have a scope. Never probed a PC processor before so will need to check datasheet for pinout. Also, is this test to be done with processor in place or removed?

Venture wrote on 2023-11-05, 09:42:

Since a couple of you are having a discussion about suitable graphics card(s) for this machine, are all the Ebay links I posted suitable? It'd be good to get some clarity on this if possible.

I dont know what pentiumspeed deal is, he really wants you to get a card suitable for gaming 😀

Venture wrote on 2023-11-05, 09:42:

Good idea. I'm in London, UK and will need to look in to this. Any members in the UK know a good hackerspace with a PC guy?

https://wiki.hackerspaces.org/London doesnt look encouraging. First one closed, second in an event space/coffee shop? Id contact http://southlondonmakerspace.org/ and ask if they can help hands on with vintage industrial computer, maybe they have a mailing list or a chat group.

Venture wrote on 2023-11-05, 09:42:

rasz_pl wrote on 2023-11-04, 21:22:

My best theory right now is ISA clock? Do you have a scope? Measure ISA pin B20 (CLK) in working 486 setup, and then again with Pentium SBC. There is a slight chance Pentium board starts with most conservative ISA divider (4-7MHz) letting video BIOS initialize, but then switching to higher clock (8MHz) resulting in garbage on screen.

Sure, I have a scope. Never probed a PC processor before so will need to check datasheet for pinout. Also, is this test to be done with processor in place or removed?

ISA pin B20 https://en.wikipedia.org/wiki/Industry_Standa … SA_Bus_pins.svg

rasz_pl wrote on 2023-11-05, 17:12:

I dont know what pentiumspeed deal is, he really wants you to get a card suitable for gaming 😀

No worries, I placed an offer on the last Ebay link for a PCI graphics card and the guy accepted so it should be here in the next couple of days. Having a simple graphics card will be useful, same as the post card.

rasz_pl wrote on 2023-11-05, 17:12:

https://wiki.hackerspaces.org/London doesnt look encouraging. First one closed, second in an event space/coffee shop? Id contact http://southlondonmakerspace.org/ and ask if they can help hands on with vintage industrial computer, maybe they have a mailing list or a chat group.

I found that yesterday. South London one is a bit far from me and the first is only 20mins from me but I'm not 100% sure if they are open. I can always email them and check I suppose.

rasz_pl wrote on 2023-11-04, 21:22:

My best theory right now is ISA clock? Do you have a scope? Measure ISA pin B20 (CLK) in working 486 setup, and then again with Pentium SBC. There is a slight chance Pentium board starts with most conservative ISA divider (4-7MHz) letting video BIOS initialize, but then switching to higher clock (8MHz) resulting in garbage on screen.

Right, thanks for the info. I've just done this and it's a bit inconclusive:

1. 486 board provides an 8MHz or so square wave. Photo attached. It does this pretty much as soon as you power up, and stays like that. The waveform looks a bit nasty, but I am not too worried about that because I am probing on an ISA connector a couple of places down from the SBC, and I'm using a bit of wire to get down in to the connector, plus I have a long ground wire attached to the case. These are probably the reason for the wobbly waveform.

2. Beeping Pentium SBC does indeed start at a much lower clock frequency, but only for a few milliseconds, then quickly reverts to 8MHz clock. Video link here. https://vimeo.com/881627944?share=copy
I am not sure if this is long enough to make the graphics card go wrong. The lower clock frequency disappears so quick that unfortunately I can't say what the lower frequency is, but guessing around 2MHz.

3. Dead Pentium SBC does the same with the clock as the beeping one.

One slightly worrying thing is that the beeping SBC now does not show any video, not even the garbage on the monitor. I think this is due to either the contacts on the board or the backplane becoming tired. It happened a couple of days ago and I re-seated the SBC and it started working again.