SupraDrive 500 Ram question...

[luvtofish]

I've got my A500 working with the SupraDrive 500 sidecar, however I have a problem with the 2MB daughter board inside the sidecar. I've been getting mysterious GME and software errors loading some programs. I downloaded and ran disksalv against the old 20MB hard disk but it checked out fine. I then ran "memtest" and found I have problems with the "external memory" bank (chip memory checked out fine). I ended up turning off the memory via the jumper on the expansion board.

The weird thing is the memory is found upon boot up and passes all of the start-up diags the A500 goes through.

My question...will replacing the 16 memory chips (1Mx1 18 pin DIP) on the expansion board solve the memory issue or could it be a problem with one of the other IC on the daughter board? There are two other chips on this board that seem kind of warm to the touch and are labeled "49-4B" and 49-5B"...could these be causing the problem?

Appreciate any help I can get on this issue!

-ltf

[danbeaver]

Could you better explain the errors? You say they occur on loading? Is that from your HDD?  Are you sure these are not I/O errors from  the hard drive?  Memory errors ought to crash the computer when running a program, shouldn't they?

[Zac67]

RAM testing on startup isn't thorough at all. Is memtest showing the bad memory bits? You can try swapping one pair of RAMs at a time, the error will move if you've got a bad one. 1Mx1 chips are easy to find used, shouldn't be too hard to replace.

[danbeaver]

They are easy to find new, as well, but jumping to conclusions is so much easier

[luvtofish]

It is crashing the computer, but only when I start launch a game or program. workbench commands work just fine.

memtest bombs out when testing the external memory. It usually happens when it starts the write test portion of the test.

I ordered replacement 1Mx1 dip's, hoping for the best.

[Zac67]

memtest bombs out when testing the external memory. It usually happens when it starts the write test portion of the test.

That sound more like an addressing problem (test data overwriting the program). Have you verified that all RAM pins make good contact into their sockets? No missed or bent pins? Solder points of the sockets in order?

[luvtofish]

All the chip pins are located within their respective sockets and none seem to be bent as far as I can tell. I have not looked at the socket themselves to see if they are loose or messed up in anyway. I'll check that next. Thanks for the tip.

[luvtofish]

Got my new 1Mx1 18 pin DIP in today for the SupraDrive daughter board. I wasted no time and jumped right in replacing all 16.

Anwhatdoyaknow!!! All is right with the world now!!!

A big thanks to all for responding!

-LTF