rootinit wrote on 2022-11-29, 02:36:

I found an AT 486 motherboard at an electronics resale shop with an included Intel A80486DX-33. I popped-in a 72-pin SIMM that I […]
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I found an AT 486 motherboard at an electronics resale shop with an included Intel A80486DX-33. I popped-in a 72-pin SIMM that I found elsewhere in the shop, and brought it home. Everything there is sold as-is, but I figured it was worth a try. I ordered an AT power supply, and inserted my Micro-Labs Ultimate VGA/TrueColor ISA card (Tseng Labs ET4000 graphics), which was working last I checked. I also swapped the CMOS battery with a new one.

Unfortunately, I got no video output, so I grabbed an ISA PC analyzer diagnostic card to get codes. It appears to stop at the "00" error code, which the manual tells me means the following: "Code copying to specific areas is done. Passing control to INT 19h boot loader next".

I believe that means it should be handing off to the disk's bootloader (no disk is here, since I have no controller card). If that were the case, shouldn't I still see some video? I wish I could troubleshoot with dip switch settings, but I have no clue what board this is (see attached images). I don't even know where to plug-in the PC speaker from the diag card. The only identifiable number that I can find on it is the following (which yields no search results on the web): 5320962-1RA0231962

Am I out of luck? What should be done next?

Kinda looks like this Dell system board - https://theretroweb.com/motherboards/s/dell-s … 6-xx-mdt-rev.-2

There's an old support page here with more info - https://web.archive.org/web/19970617044811/ht … 24M/default.htm

Maybe try the onboard video as well?

rootinit wrote on 2022-11-29, 02:36:

I found an AT 486 motherboard at an electronics resale shop with an included Intel A80486DX-33. I popped-in a 72-pin SIMM that I found elsewhere in the shop, and brought it home. Everything there is sold as-is, but I figured it was worth a try. I ordered an AT power supply, and inserted my Micro-Labs Ultimate VGA/TrueColor ISA card (Tseng Labs ET4000 graphics), which was working last I checked. I also swapped the CMOS battery with a new one.

Unfortunately, I got no video output, so I grabbed an ISA PC analyzer diagnostic card to get codes. It appears to stop at the "00" error code, which the manual tells me means the following: "Code copying to specific areas is done. Passing control to INT 19h boot loader next".

Are there any codes before? Or just 00 all the time?

I ask, because 00 sounds like the card failed to receive any code whatsoever. However, I have one of those "4 but pci/isa analyzer cards" that doesn't seem to work on my 386sx (I haven't tested it in a newer MBs ISA bus, so it might be the card). I'm not sure why that is. Another thing to try is if you're inserting the analyzer card the right way. I quadruple-checked this with my card as it doesn't have any indication which way it is supposed to go, but it does have one isa pin that is very visibly grounded so after establishing this should be pin b10 I knew how to insert it.

It would be useful to know if one can break the MB by inserting an isa card wrong way... Looking at the pinout there is all sorts of bad stuff happening then like connecting address lines and irqs directly to ground etc.

Regarding your MB, my point is your MB might be perfectly fine, but it is just the card. Did you find a jumper manual for the board? I found theretroweb.com is an invaluable resource. If you fail to find that exact model there are often similarities with other boards of the manufacturer made at the same time so look at those. It is also very useful to read the manual.

Those boards don't show errors if something is set incorrectly. They just fail to boot.

that simm doesnt look plugged in correctly, at least in the first picture
this motherboard does look Dell/HP/some other corporate vendor, dont like those

Imo main reason you dont see any video and post card says its time to boot is build-in VGA on the motherboard gets initialized as first, and afaik you cant have two ISA VGAs installed at the same time. You will need to locate pinouts and make your own VGA dongle.
good news is WDC90C31 is a VLB design, so graphics speed should be perfectly fine. never mind, I got confused by https://www.recycledgoods.com/western-digital … bus-video-card/

PC Hoarder Patrol wrote on 2022-11-29, 03:36:

Kinda looks like this Dell system board - https://theretroweb.com/motherboards/s/dell-s … 6-xx-mdt-rev.-2 […]
Show full quote

rootinit wrote on 2022-11-29, 02:36:

I found an AT 486 motherboard at an electronics resale shop with an included Intel A80486DX-33. I popped-in a 72-pin SIMM that I […]
Show full quote

I found an AT 486 motherboard at an electronics resale shop with an included Intel A80486DX-33. I popped-in a 72-pin SIMM that I found elsewhere in the shop, and brought it home. Everything there is sold as-is, but I figured it was worth a try. I ordered an AT power supply, and inserted my Micro-Labs Ultimate VGA/TrueColor ISA card (Tseng Labs ET4000 graphics), which was working last I checked. I also swapped the CMOS battery with a new one.

Unfortunately, I got no video output, so I grabbed an ISA PC analyzer diagnostic card to get codes. It appears to stop at the "00" error code, which the manual tells me means the following: "Code copying to specific areas is done. Passing control to INT 19h boot loader next".

I believe that means it should be handing off to the disk's bootloader (no disk is here, since I have no controller card). If that were the case, shouldn't I still see some video? I wish I could troubleshoot with dip switch settings, but I have no clue what board this is (see attached images). I don't even know where to plug-in the PC speaker from the diag card. The only identifiable number that I can find on it is the following (which yields no search results on the web): 5320962-1RA0231962

Am I out of luck? What should be done next?

Kinda looks like this Dell system board - https://theretroweb.com/motherboards/s/dell-s … 6-xx-mdt-rev.-2

There's an old support page here with more info - https://web.archive.org/web/19970617044811/ht … 24M/default.htm

Maybe try the onboard video as well?

You are a wizard! It is that board, and I disabled the onboard video. I then got video out! Unfortunately, after letting it sit for a moment, the screen turned white, and now the same bad behavior occurs. Not sure if this is a problem with my video card, or if this board has other problems. Will have to test with other machine(s) to make certain. Thanks again though, I have way more information than I did before. Not sure how you managed to identify it, but kudos for having a great eye/memory.

rasz_pl wrote on 2022-11-29, 05:05:

that simm doesnt look plugged in correctly, at least in the first picture

It was, I had to reseat. Unfortunately, I am having other issues. See my last response.

flynth wrote on 2022-11-29, 04:52:

Are there any codes before? Or just 00 all the time?

There are codes before. It seems to be working properly.

flynth wrote on 2022-11-29, 04:52:

It would be useful to know if one can break the MB by inserting an isa card wrong way... Looking at the pinout there is all sorts of bad stuff happening then like connecting address lines and irqs directly to ground etc.

I've read that it could, but I'm fairly certain it is inserted properly. Someone correct me if I'm wrong.

rootinit wrote on 2022-11-29, 02:36:

Not sure if this is a problem with my video card, or if this board has other problems. Will have to test with other machine(s) to make certain.

Tested the VGA card in another machine, and it works fine. This board is wonky.

might need deoxit on isa ports? have you tried plugging it out on an again? 😀

rasz_pl wrote on 2022-11-29, 06:16:

might need deoxit on isa ports? have you tried plugging it out on an again? 😀

Yeah, a few times now. Also tried swapping slots to no avail. Can't get video again. I don't have any deoxit, but would try it. Maybe I can just try cleaning with some alcohol? I am at a loss of what to do again, haha.

does the post card still show going thru all the codes all the way to 00? maybe the dip switch block is so old it lost contact making it think you witched back to integrated vga? wiggle those switches
you can look at bt475 http://wiki.xp-el.com/_media/info:brooktree_bt475.pdf and trace pins 25 26 27 to nearby header, those will be your RGB
https://www.vgamuseum.info/index.php/cpu/item … ital-wd90c31-lr datasheet 110 VSYNC 111 HSYNC

rasz_pl wrote on 2022-11-29, 08:08:

does the post card still show going thru all the codes all the way to 00? maybe the dip switch block is so old it lost contact making it think you witched back to integrated vga? wiggle those switches
you can look at bt475 http://wiki.xp-el.com/_media/info:brooktree_bt475.pdf and trace pins 25 26 27 to nearby header, those will be your RGB
https://www.vgamuseum.info/index.php/cpu/item … ital-wd90c31-lr datasheet 110 VSYNC 111 HSYNC

Weird. It was jumper settings that I modified to get it to disable onboard VGA, but toggling the dip switches back and forth got it to display a blue screen (nothing else). I toggled the dip switches again, and it's back to not working again. I also switched it to monochrome mode, and it gave me a green screen, but wasn't reproducible. Definitely some bizarre behavior happening here. I'm guessing this board was probably causing problems, and that's why it was removed from its OEM chassis.

But to answer your questions, yes, it still goes through all the codes no matter what. When it gave the blue screen it stopped on a different code though (2C, "All necessary processes before passing control to the video ROM are done. Next, look for the video ROM and pass control to it" ). I don't get that code when nothing is displayed on the screen. I get code 13 (disabled video) followed by a 00.

I've been further testing and documenting. Not expecting anyone to give me a response or solution, just wanted to document here. Turning it on after being cold seems to make it more reliable to boot. After it warms-up, and I restart it, it tends to have the no video problem. I've documented the codes that are reported from the ISA diagnostic card in both situations. They are two very different sequences of codes. The descriptions of the codes are transcribed from the PC Analyzer's user guide, and are probably poor Chinese translations, but they are included for reference.

One other thing that I've noticed is that when it does show video, the amount of detected memory is reported as seemingly random different numbers.

Boot sequence to BIOS screen (video is output properly):

1. 26 None
2. 27 Any initialization before seething video mode will be done next.
3. 28 Initialization before setting the video mode is complete.
4. 29 None
5. 2A Initialize the different bus system, static, and output devices, if present.
6. 26 None
7. 2C All necessary processes before passing control to the video ROM are done. Next, look for the video ROM and pass control to it.
8. 2D The video ROM has returned control to BIOS POST. Performing any required processing after the video ROM had control.
9. AA Initialization after E000 option ROM control has been completed. Displaying the system configuration next.
10. 2E Completed post-video ROM test processing. If the EGA/VGA controller is not found performing the display memory Read/write test next.
11. 35 None
12. 36 None
13. 37 The display mode is set. Display the power on message next.
14. 38 Initialize the bus input, IPL general devices next, if present.
15. 39 Display bus initialization error messages.
16. 3A The new cursor position has been read and saved. Display the Hit (DEL) messages next.
17. 36 None
18. 40 Preparing the 4 descriptor tables.
19. 41 None
20. 42 The descriptor tables are prepared. Entering protected mode for the memory test next.
21. 43 Enter protected mode. Enable interrupts for diagnostics mode next.
22. 44 Interrupts have been enabled (if the diagnostics switch is on, then initialize date to check memory wraparound at 0:0)
23. 45 Date initialized. Check for memory wraparound at 0:0 and find the total system memory size.
24. 46 The memory wraparound is done. Memory size has been calculated, which will be written into the patterns to test memory.
25. 47 The memory pattern has been written to extended memory. Write patterns to the base 640KB memory next.
26. 48 Patterns written in base memory. Determine the amount of above 1MB next.
27. 49 The amount of memory below 1MBhas been found and verified. Determine the amount of memory above 1MB next.
28. 4A None
29. 46 The memory wraparound is done. Memory size has been calculated, which will be written into the patterns to test memory.
30. 4E The memory test started, but not as a result of a soft reset. Display the first 64KB memory size next.
31. 4F The memory size display has started. The display is updated during the memory test. Perform the sequential and random memory test next.
32. 50 The memory below 1MB has been tested and initialized. Adjust the displayed memory size for relocation and shadowing next.
33. 51 The memory size display was adjusted for relocation and shadowing next.
34. 52 The memory above 1MB has been tested and initialized. Save the memory size information next.
35. 53 The memory size information and the CPU registers are saved. Enter real mode next.
36. 55 None
37. 56 None
38. 58 The memory size was adjusted for relocation and shadowing, adjust the memory size next.
39. 59 The hit <DEL> message is cleared. The <WAIT...> message is displayed. Next start the DMA and interrupt controller test.
40. 55 None
41. AA Initialization after E000 option ROM control has been completed. Displaying the system configuration next.
42. 0F The initialization after the keyboard controller BAT command test is done. The keyboard command byte is written next.
43. 00 Code copying to specific areas is done. Passing control to INT 19h boot loader next.
44. 55 None
45. AA Initialization after E000 option ROM control has been completed. Displaying the system configuration next.
46. 0F The initialization after the keyboard controller BAT command test is done. The keyboard command byte is written next.
47. 00 Code copying to specific areas is done. Passing control to INT 19h boot loader next.
48. 60 The DMA page register test is passed. Perform the DMA Controller 1 base register test next.
49. 61 None
50. 62 The DMA controller 1 base register test is passed. Perform the DMA controller 2 base register test next.
51. 63 None
52. 64 None
53. 65 The DMA controller 2 base register test passed. Programming DMA controllers 1 and 2 next.
54. 66 Completed programming DMA controllers 1 and 2. Initializing the 8259 interrupt controller initialization.
55. 67 Completed 8259 interrupt controller initialization.
56. 80 The keyboard test has started. Clear the output buffer and check for stuck keys. Issue the keyboard rest command next.
57. 81 A keyboard reset error or stuck key was found. Issue the keyboard controller interface test command next.
58. 82 The keyboard controller interface test is completed. Write the command byte and initialize the circular buffer next.
59. 83 The command byte was written and global data initialization has been completed. Check for a locked key next.
60. 85 The memory size check is done. Display a soft error and check for a password or bypass WINBIOS setup next.

Here is a grab of what is displayed on the screen when that is done.

Boot sequence to blank screen (no video output):

1. 01 None
2. 02 None
3. 03 Disable NMI PIE, AIE UEI, and SQ. The NMI is disabled. Next, check for a soft reset or a power on condition.
4. 05 The BIOS stack has been built. Next disable cache memory.
5. 06 The uncompress the POST code.
6. 07 Next initialize the CPU and the CPU data area.
7. 08 The CMOS checksum calculation.
8. 09 None
9. 0A The CMOS checksum calculation is done. Initializing the CMOS status register for dae and time next.
10. 06 Then uncompress the POST code.
11. 0C The keyboard controller input buffer is free. Next, issue the BAT command to the keyboard controller.
12. 0D None
13. 0E The keyboard controller BAT command result has been verified. Next, perform any necessary initialization after the keyboard controller BAT command test.
14. 0F The initialization after the keyboard controller BAT command test is done. The keyboard command byte is written next.
15. 10 Test DMA. The keyboard controller command byte is written. Next, issue the Pin 23 and 24 blocking and unblocking command.
16. 11 Next, check if <END> or <INS> keys were pressed during power on. Initialization CMOS RAM in every boot AMIBIOS POST option was set in AMIBCP or the <END> key was pressed.
17. 12 Next, disable DMA controllers 1 and 2 and interrupt controllers 1 and 2.
18. 13 The video display has been disabled. Port B has been initialized. Next initialize the chipset.
19. 00 Code copying to specific areas is done. Passing control to INT 19h boot loader next.
20. 13 The video display has been disabled. Port B has been initialized. Next initialize the chipset.
21. 00 Code copying to specific areas is done. Passing control to INT 19h boot loader next.
22. 13 The video display has been disabled. Port B has been initialized. Next initialize the chipset.
23. 00 Code copying to specific areas is done. Passing control to INT 19h boot loader next.

http://mrbios.com/techsupport/award/postcodes.htm "AMI WinBIOS; 12/15/93 Onwards"

Were you resetting instead of powering off? that would explain second sequence being shorted, doesnt need to detect any hardware/ram if its a warm reboot.

- Counting memory wrong + first picture with badly seated simm - maybe sim socket is damaged? it wont necessarily be visible, try one simm in different one.
- Measure 5V on the vga card when it doesnt show any picture
- put few books under the motherboard so its fully supported laying flat and vga card bracket can hang loose, discharge yourself (touch metal pipes in the house), press with one finger one chip at a time (start with big OPTI ones) and power system on while pressing that chip, go to the next until maybe you find something funny
- trace the pins I gave you earlier to that header near WDC chip and make VGA dongle, test if same thing happens with integrated graphics