VOGONS


First post, by NScaleTransitModels

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I picked up an untested Socket 4 motherboard with many missing components, labeled Biostar MB-1566-PAT-A. After replacing the cache, memory, CPU, and keyboard BIOS, I was able to bring it partially back to life.

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It came without the keyboard BIOS chip, so I pulled one from another motherboard I have. Thing is, all the socketed chips I have are this model:

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Swapping in this keyboard BIOS, I am able to get the mobo to start. However, the keyboard is very unresponsive. On each boot, I'm only able to get one or two delayed keystrokes in before the keyboard quits. Probably because this model of keyboard BIOS is incompatible.

Since I don't have any other socketed keyboard BIOS chips to try, I'll have to buy a replacement. Does anyone here have experience transplanting these keyboard BIOS chips? Which brand might be worth a try— AMIKEY, JETKEY, VIA etc? Unfortunately I was unable to find reference photos of this exact mobo with the keyboard BIOS present. Thanks in advance.

Builds:

  • ECS FX-3000; 386DX-40@50; ET4000AX, ISA 1mb
  • Acer VI9; 486DLC-40; Mach32, VLB 2mb
  • Chicony CH-471A; CX486s-40; Mach32, VLB 2mb
  • Gateway 2000 P5-60; Pentium-60@66; S3 928, PCI 3mb
  • DTK PKM-0033S; AM5x86-133@160

Reply 2 of 7, by jakethompson1

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Not sure how much it helps but some of the other boards with that chipset do have pictures: https://www.ultimateretro.net/en/motherboards/?chipsetId=665
I see AMIKEY and VIA.
Which BIOS is your "regular" BIOS on this board?
I have a copy of "Programmer's Guide to the AMIBIOS" and from what I remember, an "incorrect" keyboard BIOS shouldn't cause as severe as problems as you say, but it will break power management features.

Reply 3 of 7, by NScaleTransitModels

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majestyk wrote on 2022-07-24, 15:47:

Have you found out what´s missing at the top-right corner? I hope it´s not a PAL (like U29)...

I think it's the "dirty tag". Not sure what it does, and I've never seen it on any other motherboards. From the manual:
"The dirty tag is optional and may not be on all boards. The location is unidentified."

jakethompson1 wrote on 2022-07-24, 15:57:
Not sure how much it helps but some of the other boards with that chipset do have pictures: https://www.ultimateretro.net/en/mot […]
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Not sure how much it helps but some of the other boards with that chipset do have pictures: https://www.ultimateretro.net/en/motherboards/?chipsetId=665
I see AMIKEY and VIA.
Which BIOS is your "regular" BIOS on this board?
I have a copy of "Programmer's Guide to the AMIBIOS" and from what I remember, an "incorrect" keyboard BIOS shouldn't cause as severe as problems as you say, but it will break power management features.

The VIA VT82C42N is available on Ebay, so it might be worth a shot. My ROM BIOS is Award, which I thought may have compatibility problems w/ the keyboard BIOS I'm currently trying (American Megatrends).

If the VIA part doesn't work either, I'm thinking it may be a blown fuse F1 or a loose keyboard connector.

Here are some screenshots, if they may help. This is as far as I get before the keyboard quits.

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thumbnail_20220724_134747.jpg
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Builds:

  • ECS FX-3000; 386DX-40@50; ET4000AX, ISA 1mb
  • Acer VI9; 486DLC-40; Mach32, VLB 2mb
  • Chicony CH-471A; CX486s-40; Mach32, VLB 2mb
  • Gateway 2000 P5-60; Pentium-60@66; S3 928, PCI 3mb
  • DTK PKM-0033S; AM5x86-133@160

Reply 4 of 7, by jakethompson1

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NScaleTransitModels wrote on 2022-07-24, 21:07:
majestyk wrote on 2022-07-24, 15:47:

Have you found out what´s missing at the top-right corner? I hope it´s not a PAL (like U29)...

I think it's the "dirty tag". Not sure what it does, and I've never seen it on any other motherboards. From the manual:
"The dirty tag is optional and may not be on all boards. The location is unidentified."

A write-back cache intercepts writes from the CPU to memory and only updates the cache, intentionally allowing memory to become stale vs. the most current data in the cache in exchange for higher performance. Rather than having devices that read directly from memory like ISA DMA devices (like floppy controller) or PCI bus mastering devices (like SCSI controllers or Intel Triton IDE) go to the cache instead, a scheme is implemented where their access to/from memory is intercepted and if fresher data is in cache, it is written back to memory before their access is allowed to resume.

The dirty bit tracks whether the data in cache and memory have become out of sync. Some of these chipsets can or must use a separate dirty RAM like this. The alternative is to rob a bit from the tag RAM, cutting the cacheable area in half, or to hardwire the dirty bit, causing needless writes back to memory even when the cache is unchanged and therefore hurting performance.

Reply 5 of 7, by evasive

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We have some info here:
https://www.ultimateretro.net/it/motherboards/1102
If you have a full manual, yes please, if you can manage to make a backup of the bios, yes please. Some people at x86 box might be able to figure out what keyboard bios goes with your bios.

Reply 6 of 7, by rasz_pl

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jakethompson1 wrote on 2022-07-24, 15:57:

I have a copy of "Programmer's Guide to the AMIBIOS" and from what I remember, an "incorrect" keyboard BIOS shouldn't cause as severe as problems as you say, but it will break power management features.

I recall someone repairing a board on vogons and stumbling on two different keyboard controllers expecting different clocks, one was 8mhz the other 12MHz

Reply 7 of 7, by BurnedPinguin

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NScaleTransitModels wrote on 2022-07-24, 21:07:
I think it's the "dirty tag". Not sure what it does, and I've never seen it on any other motherboards. From the manual: "The dir […]
Show full quote
majestyk wrote on 2022-07-24, 15:47:

Have you found out what´s missing at the top-right corner? I hope it´s not a PAL (like U29)...

I think it's the "dirty tag". Not sure what it does, and I've never seen it on any other motherboards. From the manual:
"The dirty tag is optional and may not be on all boards. The location is unidentified."

jakethompson1 wrote on 2022-07-24, 15:57:
Not sure how much it helps but some of the other boards with that chipset do have pictures: https://www.ultimateretro.net/en/mot […]
Show full quote

Not sure how much it helps but some of the other boards with that chipset do have pictures: https://www.ultimateretro.net/en/motherboards/?chipsetId=665
I see AMIKEY and VIA.
Which BIOS is your "regular" BIOS on this board?
I have a copy of "Programmer's Guide to the AMIBIOS" and from what I remember, an "incorrect" keyboard BIOS shouldn't cause as severe as problems as you say, but it will break power management features.

The VIA VT82C42N is available on Ebay, so it might be worth a shot. My ROM BIOS is Award, which I thought may have compatibility problems w/ the keyboard BIOS I'm currently trying (American Megatrends).

If the VIA part doesn't work either, I'm thinking it may be a blown fuse F1 or a loose keyboard connector.

Here are some screenshots, if they may help. This is as far as I get before the keyboard quits.
thumbnail_20220724_134628.jpg
thumbnail_20220724_134747.jpg

As counter-intuitive as it may sound, there are instances of AwardBIOS (mostly ASUS) that actually require an American Megatrends keyboard controller. The one you tried is an AMIKEY-2, which is pretty much the ultimate as far as compatibility goes. It is fully backwards compatible with the original AMIKEY, and it and the second edition were cloned loads. So it's very likely that whatever this motherboard expects can be fulfilled by the AMIKEY-2.

With this knowledge I can at least conclude that the KBC you tried already should work fine in that board, and you might want to seek problems elsewhere, for that I cannot help, but I'm sure others in there probably can.