There's a bios for a motherboard using the same chipset as yours. Maybe you can give it a try ? http://www.win3x.org/uh19/motherboard/show/2047

2. You're right, 32.768kHz crystal for the RTC. Should be really easy to find.
3. I'm 99% certain that the socketed chip is the PLL clock generator. On AmoRetro's pic I can see it's made by Macronix but it's really hard to tell the part number. Luckily you're not missing the other socketed IC (the PAL).

quicknick wrote on 2020-12-25, 01:09:

2. You're right, 32.768kHz crystal for the RTC. Should be really easy to find.
3. I'm 99% certain that the socketed chip is the PLL clock generator. On AmoRetro's pic I can see it's made by Macronix but it's really hard to tell the part number. Luckily you're not missing the other socketed IC (the PAL).

#3: mx8315pc (if same as on my similar but diff model Biostar). Yes very lucky the PAL chip is there !
Wondering why the the VRM trannies and resistors were removed, only guess is to fix similar but the removal of the resistors seems odd as they do not break down or burn up....

Maybe it was used for parts ? I've seen this before

Deksor wrote on 2020-12-24, 23:16:

There's a bios for a motherboard using the same chipset as yours. Maybe you can give it a try ? http://www.win3x.org/uh19/motherboard/show/2047

Thanks! Will try that.

Horun wrote on 2020-12-25, 03:33:

#3: mx8315pc (if same as on my similar but diff model Biostar). Yes very lucky the PAL chip is there !
Wondering why the the VRM trannies and resistors were removed, only guess is to fix similar but the removal of the resistors seems odd as they do not break down or burn up....

Is there an alternative for that mx8315pc part? I can't find a chip to buy online, but I'll look at my other boards later for a possible replacement.

quicknick wrote on 2020-12-25, 01:09:

2. You're right, 32.768kHz crystal for the RTC. Should be really easy to find.

Is there a ceramic capacitor underneath it?

jheronimus wrote on 2020-12-26, 01:25:

Horun wrote on 2020-12-25, 03:33:

#3: mx8315pc (if same as on my similar but diff model Biostar). Yes very lucky the PAL chip is there !
Wondering why the the VRM trannies and resistors were removed, only guess is to fix similar but the removal of the resistors seems odd as they do not break down or burn up....

Is there an alternative for that mx8315pc part? I can't find a chip to buy online, but I'll look at my other boards later for a possible replacement.

Quest Components has them, that is where I bought some Dallas RTC a few months ago that work perfectly.
They have over 200 in stock, the part is discontinued but will be NOS and when gone there be no more....
https://www.questcomp.com/part/4/mx8315pc/279851702
at $2.60 each plus shipping. If you need any Dallas RTC they still have some, type DS12887 and DS12c887 into search box for a list.
I will double check Digikey and Mouser as they have Euro distributes too. I may order a few of those myself.
Edit: nope only found at Quest so far. The UMC9515 is an equal part according to mkarcher but cannot find any in stock.

jheronimus wrote on 2020-12-26, 01:25:

Is there a ceramic capacitor underneath it?

Yes, but it's not missing on your board from what I can see...

Wow, missing resistors next to the VRMs are a nasty surprise. What kind of resistance should they have?

Here's what I found for LT-1085CT (upper, responsible for providing 5V to ISA) and LT-1084CT (lower, responsible for providing 3.3V to the CPU).

Am I correct to assume that both should work with 0.25W resistor for 120 Ohm and a 0.25W for 360 Ohm?

So I came back to this project, ordered mx8315pc from eBay and found a guy that will (hopefully) be able to fix the board, but he will only be able to start in May at the earliest. He already fixed a Supermicro P54VL-PCI for me, so I figured that it's a better idea than trying to fix the Biostar board myself.

Meanwhile I'm still trying to find the original BIOS. So far I have only figured that the BIOS string should be 2A5UMB01 and be 128KB in size. I have contacted Biostar for a BIOS, but they replied that they don't have anything on this board anymore. FGB, the author of amoretro, says he doesn't have the board anymore.

So I'm bumping the thread in hopes that somebody notices it and could provide me with a dump of the original BIOS 😀 If that doesn't work, I'll of course try the BIOS from another board using Opti 546/547 chipset, but from my experience with an Opti 596/597, an alternative BIOS might not be too stable.

У меня есть такая мать. Рабочая.

--- Google Translate ---

I have such a mother. Working.

Reystlin wrote on 2021-07-01, 12:48:

https://i.postimg.cc/GpRtD8Vx/IMG-20210701-005546-1.jpg У меня есть такая мать. Рабочая. --- Google Translate --- I have such a […]
Show full quote

У меня есть такая мать. Рабочая.
--- Google Translate ---
I have such a mother. Working.

Привет! А можно тебя попросить снять образ биоса и прикрепить к сообщению?

Я свою полностью восстановил, только биос и остался.

--- Google Translate ---

Hey! Can I ask you to remove the BIOS image and attach it to the message?

I completely restored mine, only the bios remained.

Ща попробую. Программатор есть. Но я не знаю, как тут сообщения прикреплять.

--- Google Translate ---

I'll try. There is a programmer. But I do not know how to attach messages here.

Reystlin wrote on 2021-07-01, 13:13:

Ща попробую. Программатор есть. Но я не знаю, как тут сообщения прикреплять.

--- Google Translate ---

I'll try. There is a programmer. But I do not know how to attach messages here.

Можно через дропбокс/яндекс/гугл драйв расшарить и вставить ссылку.

Либо просто аттачментом к сообщению — это есть, если перейти в полный редактор

--- Google Translate ---

You can share and insert a link through dropbox / Yandex / Google Drive.

Or just an attachment to the message - this is, if you go to the full editor

jheronimus wrote on 2021-07-01, 13:35:

Можно через дропбокс/яндекс/гугл драйв расшарить и вставить ссылку. […]
Show full quote

Reystlin wrote on 2021-07-01, 13:13:

Ща попробую. Программатор есть. Но я не знаю, как тут сообщения прикреплять.

--- Google Translate ---

I'll try. There is a programmer. But I do not know how to attach messages here.

Можно через дропбокс/яндекс/гугл драйв расшарить и вставить ссылку.

Либо просто аттачментом к сообщению — это есть, если перейти в полный редактор

--- Google Translate ---

You can share and insert a link through dropbox / Yandex / Google Drive.

Or just an attachment to the message - this is, if you go to the full editor

На дропбоксе регаться надо. Лень. Залил на какой-то filesend
Ссылку на BIOS оставил в сообщении выше. Пробуй.
Если что - у меня MB-1500PCT-A rev.2 Надеюсь это оно.
Удачи в запуске!

ЗЫ: Микруха на BIOSе стояла TMS27C010A (если вдруг интересно)

--- Google Translate ---

It is necessary to register on the dropbox. Laziness. Uploaded to some filesend
The link to the BIOS was left in the message above. Try it.
If that - I have MB-1500PCT-A rev.2 I hope this is it.
Good luck with your startup!

PS: Microcircuit on BIOS was TMS27C010A (if suddenly interested)

Link above seems dead (redirects to the same page), could any of you upload it again ?

computerguy08 wrote on 2021-07-01, 14:12:

Link above seems dead (redirects to the same page), could any of you upload it again ?

It just asks for captcha twice for some reason. Attached the file to this message

Reystlin wrote on 2021-07-01, 13:47:

Удачи в запуске!

--- Google Translate ---

Good luck with your startup!

Cпасибо огромное, буду в выходные тестить. Полгода искал считай 😀)

--- Google Translate ---

Thank you very much, I will be testing this weekend. I was looking for half a year 😀)

Thank you!

Added photo and BIOS image on uh19: http://www.win3x.org/uh19/motherboard/show/1134

Holy shit, it actually works.

Having the original BIOS was critical for this board because it really fixed a number of issues:

1) somehow the video output wasn't stable with a WinTech BIOS. The image was literally shaking slightly
2) I can now use 1MB of cache which didn't work before no matter the settings/configuration. Guess I'll have to find 16 pcs of 128k x 8 SRAM chips now for 2MB
3) I can now use the tightest cache and RAM timings, all the way down to 3-2-2-2

I'm really happy these issues got fixed because I was worried that I've picked the wrong replacement for the missing components.

Somehow the board still doesn't work with EDO RAM (unlike my Supermicro P54VL-PCI that uses the previous Opti "Premium" chipset) and it only works with original Pentiums. Pentium MMX Overdrive is detected as 486DX-66 and results in horrible performance in Quake. IDT WinChip, AMK K5 and AMD K6-2 (using an Evergreen Spectra upgrade) won't boot at all. Oh well, there goes my plan to make an outrageously unreasonable AMD K6-based VLB system 😀

I'll make a post with a complete build with benchmarks once I finish it.