VLIW wrote on 2024-08-29, 19:02:

I tried Siemens HYB514256B-60 in the four slots with no luck. BIOS still listed 512 KB.

This is surprising. These chips should be the correct model.

VLIW wrote on 2024-08-29, 19:02:

To make sure - in which orientation are the DIP20 chips supposed to be inserted?

As your picture is taken: Pin 1 to the lower left. Marking of the chips upright (not upside-down). There is a white dot next to pin 1, and an indentation on the left side of the socket indicating pin 1 and 20 going to that side.

markings on PCB suggest the chips go pin1 in bottom left corner like the existing chips do.

The Siemens chips should have worked though, they have the correct pinout and organization.

Thanks ^. I will retry the Siemens RAM but they were of questionable origin.

Did not find any jumpers to set or options in BIOS to modify - anything might be needed there?

It should be automatic, nothing needing to be done other than putting the chips in.

Tried with another set of DRAMs, success this time! Now with 1 MB VRAM on the 486SX33
MB81C4256A-70P

Nice, 5428 doesn't make sense with less than 1 MB.

With more than 1 MB... expanding it to 2 MB only adds two interlaced modes, so... doesn't make sense, either 🤣

VLIW wrote on 2024-09-22, 11:28:

Tried with another set of DRAMs, success this time! Now with 1 MB VRAM on the 486SX33
MB81C4256A-70P

I see remarked chips... I imagine previous ones were like it too ? Anyway congrats ~

I actually received 16x DRAMs for this sort of use case from Utsource last week... and they turned out to be 5 different kinds of chips that were all lasered to same markings and out of 16, only 6 worked, rest were damaged or perhaps not DRAMs at all... very cheap but also very very disappointing. I have not yet heard back, but it was the weekend when I voiced my complaints...

Tiido wrote on 2024-09-23, 00:27:

I see remarked chips... I imagine previous ones were like it too ? Anyway congrats ~

Yes it's super hard to get at least semi-proper chips like these. Sorry for your bad experiences, I'm also looking for a more solid source for these.

yeah.. theres so many fake chips outthere.. didn't be surprised that the other chips you used where with problems.. at least one..so.. no 1MB ram.