Troubleshooting EGA card on a NuXT \ VOGONS

Troubleshooting EGA card on a NuXT

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First post, by jal

Posted on 2023-09-28, 18:16

jal Offline

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This is a long shot, but anyway...

I've purchased an EGA card (this one, looking exactly like Vlask's Paradise Systems PEGA2A) on eBay which the seller said they've tested. When I tried it in my NuXT however, the computer doesn't boot. It hangs right after the memory check. According to the BIOS listing, after memory check it searches for option ROMs. Of course the EGA has ROM on it, but I'd expect if the ROM was at fault, I wouldn't have output on my screen at all (the video ROM is searched for and intialized). So, the BIOS hangs itself most likely during the scan for option ROMs (there's a single one in the NuXT, for the IDE BIOS - but when I disable searching for the F000 range, it still hangs).

(Note that the NuXT works fine with either the built-in PC/104 Trident VGA or an ATi Small Wonder Graphics Solution CGA/Plantronics clone.)

Anyone here by any chance have experience with EGA clone cards in a NuXT? Did they run smoothly? Anyone has any idea what could be wrong with this combo of EGA and NuXT?

JAL

Reply 1 of 4, by keenmaster486

Posted on 2023-09-28, 19:49

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Memory conflict with the ROM? Something else trying to load at that same address? XT-IDE?

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Reply 2 of 4, by the3dfxdude

Posted on 2023-09-28, 19:53

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You're getting a screen or looking at POST codes? Does the BIOS emit POST codes, and you confirmed where it hangs? If the EGA is working to that point and you can confirm a hang in BIOS, I'd contact the maker of the NuXT.

Reply 3 of 4, by jal

Posted on 2023-09-29, 07:18

jal Offline

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keenmaster486 wrote on 2023-09-28, 19:49:
Memory conflict with the ROM? Something else trying to load at that same address? XT-IDE?

I tried disabling the search for extension ROMs after F0000 (where the XT-IDE ROM resides), but to no avail.

the3dfxdude wrote on 2023-09-28, 19:53:
You're getting a screen or looking at POST codes? Does the BIOS emit POST codes, and you confirmed where it hangs? If the EGA is working to that point and you can confirm a hang in BIOS, I'd contact the maker of the NuXT.

I'm getting screen output, up until the memory check. I checked the BIOS source, and right after that check, it's doing the search for extended ROMs. With a CGA clone, it then finds the F0000 XT-IDE option ROM, but even if I disable that, it still hangs. So my best bet is that the EGA ROM on that card extends beyond its supposed range of C0000-C7FFF, since the option ROM search starts at C8000, and the BIOS thinks it's a valid option ROM, calls the init routine, and hangs the PC.

JAL

Reply 4 of 4, by jal

Posted on 2023-12-24, 20:39

jal Offline

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Small update: after purchasing a BIOS POST card, I can confirm that it hangs right after starting searching for option ROMs (code 40). Still uncertain what could cause this, it must hang in the extension_scan routine, or else I'd have a 41/42/43, but that's a fairly simple routine that can't really cause a hang.

JAL

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