I don't know whether the difference is significant. The ROM needs to be unpacked into RAM, so this would pose the question of whether there are any dependencies related to specific RAM addresses. I would think that the code would just crash if that were the case, but maybe this is all a red herring. Did you check the stickers on the back?

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A backup a day keeps DR away.

i just bought another one with the same serial number on sticker... Fingers crossed

second donor board in, now with same numbers... I changed the eprom, cleaned everything but the thing wont spin after plugging it in... Whats next? Maybe the motor is burned?

one thing that I noticed on the new board, is that one of the components seem damaged? Its the component on the far right that says "AZ"

Update: I double checked the EPROM pins that I soldered and did a continuity test to the next contact. One of the pins wasn't soldered properly so after fixing this, bingo, the HDD turned on and I was able to see the data and now its being transfered!

The new SDRAM is a 512Mbit part. I don't know if matching its capacity was absolutely necessary, but congratulations anyway.

A3R12E40CBF, Zentel, 512Mbit DDR2 SDRAM, 16M words × 8 bits × 4 banks, 1.8V, 84-ball FBGA:
https://www.zentel-europe.com/datasheets/A3R12E340CBF_v1.2.pdf

_________________
A backup a day keeps DR away.

Thanks a lot for your help! I am glad I found this forum... I almost feel like this needs to be my new hobby lol.