It probably is an EPROM but you can use a NOR flash in place of it if once pinout is made compatible (most flashes have very slightly different pinout from EPROMs). EPROM you will not be able to overwrite without a dedicated eraser and a programmer device, flash chip you can do with a programmer or hotsocketing on some random computer mobo supporting the particular chip.

Found chip from winbond: W27C512
Datasheet: http://www.kosmodrom.com.ua/pdf/W27C512-45Z.pdf

It seems to be EEPROM with exact pinout to existing EPROM: M27C512
Datasheet: https://www.bucek.name/pdf/27c512.pdf

Am i correct about this? Next step is to find a way to program it, right?

It would work in place on an EPROM. Then yes, next step is finding a way to actually program one. This is an early chip that isn't JEDEC compatible and cheapo programmers might be incapable of programming it, you'll have to scan through the supported chips list to find out if they can do it or not.

Thank you, Tiido! ... once again!

Next challange is to find the bios binary for that thing... Will be fun few unslept nights. 😜

I might have this board, BIOS included. Mine is labeled "025N2". Please post a picture of it to check if it's the same.

quicknick,
Mine has also a sticker labeled "025N2" so i think it's a match!

When i get home, i'll make a picture of it. But most notably, it's the SY-25 motherboard WITHOUT the 3.xx V power regulator in place. (So non-"P" version, i think)

Any chances for you to get the bios image off from your motherboard? 😀

check this out
https://www.infania.net/misc/moboarchive/Soyo … /486/index.html

https://web.archive.org/web/19980210113746/ht … IOS/486Bios.htm

arteq,

I've found that first link. Thanks for the second one.

It somewhat confuses me, is the 25R bios meant for my 25N as well? I have downloaded it and waiting for chips to arrive so i can burn it on, but i'm not really sure it's the right bios image...

no risk if you use wrong bios , you will just don't get POST,
but as far as i know this should works

Here's the BIOS from my "025N2"

Edit: included the 025P2 BIOS in the archive, it's somewhat newer, and if you say it's the same board it might just work.
Also, I might be wrong, but isn't R2 based on UMC chipset? N2/P2 are SiS, so chances are slim that the R2 BIOS will work.

quicknick, Thank you for the upload! As i haven't still be able to source the bios by model name (only this 25R version, not 25N), you might have just saved that motherboard of mine. Thank you!

arteq, I hope that as well, we'll see. I have 2 chips coming on my way and have a friend with appropriate programmer for these chips. We'll see how it goes. Thank you.

Okay, some time has passed, but i got myself a chip burner and was able to test other bioses.

Unfortunately the board isn't resurrected yet. The other bioses, i tried, were 25p2-j1; Soyo 486VESA (025P2) and Soyo 025N2, that have gone through this thread.
I was also able to read the original bios off from the original bios chip and the content looks fine (human readable strings inside binary are okay).

So it seems the bios chip was not the culprit.

So, current symptoms:
* No beeps
* Diag. card code: 00--
* Diag. card leds: -12V on, +12V on, +5V on, +3.3V on, CLK on, IRDY off, FRAME on, RESET off
* All keyboard leds are on
* No video signal through video card.
* CPU does get hot.

Tried multiple processors and ram sticks just in case though i know they are fine.

NB: I've attached the original bios that i did read off from the original bios chip. Maybe one day someone finds it useful. 😀
What there is i could try to investigate fruther now?

GigAHerZ wrote:

Okay, some time has passed, but i got myself a chip burner and was able to test other bioses. […]
Show full quote

Okay, some time has passed, but i got myself a chip burner and was able to test other bioses.

Unfortunately the board isn't resurrected yet. The other bioses, i tried, were 25p2-j1; Soyo 486VESA (025P2) and Soyo 025N2, that have gone through this thread.
I was also able to read the original bios off from the original bios chip and the content looks fine (human readable strings inside binary are okay).

So it seems the bios chip was not the culprit.

So, current symptoms:
* No beeps
* Diag. card code: 00--
* Diag. card leds: -12V on, +12V on, +5V on, +3.3V on, CLK on, IRDY off, FRAME on, RESET off
* All keyboard leds are on
* No video signal through video card.
* CPU does get hot.

Tried multiple processors and ram sticks just in case though i know they are fine.

NB: I've attached the original bios that i did read off from the original bios chip. Maybe one day someone finds it useful. 😀
What there is i could try to investigate fruther now?

try to re-set your cache chips and double check your CPU and cache jumpers.
try with a 5v CPU like 486dx33 or 50.

@Intel486dx33, this board is only 5V capable. I've tried both 486sx (2x25MHz) and 486dx2 (2x33MHz). Jumpers are correct, cache chips have been changed already numerous times. (And those chips do work on other boards)

I don't think there's a connection problem... there's actually something wrong with this board, but what?

Could be a cold solder joint somewhere. That was my issue on several boards. The next best case is a bad discrete component. The worst case is a faulty chipset. Enjoy the process!

I went through a board like this, pretty much turned it upside down including replacing the chipset, in the end it was a scorched tantalum capacitor and a few bent pins inside the zif socket, I guess in your case its a simple socket which can't get bent pins inside but the moral of the story is attack the easy straight forward stuff before doing pointless big things.

some quick things to check are always:
1. Visual inspection of all the caps traces, especially around the battery, check a few times and with magnifying glass you would be suprised how easy it is to miss things that stick out plainly.
2. Multimeter check the power rails, power plug, isa slot, check if 5v is inside the cpu socket
3. touch the chipsets see if they overheating, gently strike each pin on the chipset and any other smd chip with a toothpick to see if the legs are lose (you can't tell by just looking)
4. gently flex the board in a few different spots see if it brings it to life.
5. Like feipoa said enjoy the process

I've given up on this board. I currently have no ideas what to test further to make sense what is going on.
I also just got a similar board with VRM. (SY-25P2) It works and i was able to use 486DX4-100 on it. (With this board in topic, i planned to use 486DX2-66) Therefore i have my 486 completed now.

If you have any idea, what to test to maybe debug it further or confirm that this board is maybe dead on chipset level, you can throw your ideas here. I might try something out.

But all in all, this topic is mostly ended now, with sad ending. 🙁

Missed the "all the keyboard leds are on" symptom. Could be the keyboard controller, you can easily try with another KBC chip if it's socketed.

I would certainly try another keyboard controller chip. Is this board SiS 471 based ?