Upgrading C103175 Rev. 1 520STFM to 1MB - how exactly?

[jurassicman]

No way... I did some more search and I checked all I was able to check.

On the left side of the mainboard, near the MMU the pads CE, A17 and A16 are close on 1MB position. The pads W3 and W4 are close and the pad W2 is open (I don't know if all these pads are related to the RAM, though).

As per the RAM chips, I did check the voltage on pin 10 and it is +5V on all chips.
Also I did check RAS (pin 4) and CAS (pin 17) signals.

RAS continuity is present among all chips of each columns (chips 1,2,3,4 and chips 5,6,7 and 8).
CAS continuity is present in couples (between chips 1 and 2, chips 3 and 4, chips 5 and 6, chips 7 and 8).

Here some pictures and an the pinout of the RAM chip.







I really need some hints...

[rubber_jonnie]

You can ignore the jumpers, they have nothing to do with RAM and simply set the ROM IC sizes depending on whether it's a 2 or 6 chip set. Those near the Blitter just determine if one is fitted or not.

[jurassicman]

Oh! Finally I did it... it was a defective chip, at least I think so...

I fortunately bought 5 chips. I did try to replace each of them with the spare one and now I got 1MB!

[DoG]