Mac SE/30 not seeing all of the installed RAM

[JYewman]

Hi everyone,

I've seen this issue come up before, and I've also seen Adrian's Digital Basement video fixing exactly the issue I'm facing. However, I can't seem to get my SE/30 to see more than 2MB of RAM. I have 4 x 1mb sticks installed in Bank A as well as 4 x 256k stick in Bank B and my SE/30 only reports 2MB! I have checked the traces for SIZ0/SIZ1 from the GLUE and they are both fine, I've also reflowed the GLUE chip and I'm still getting the same issue.

It seems that my SE/30 thinks that I have 256k RAM sticks installed (no matter what size sticks I put in). I do get it to boot, but it reports 2MB within System 7. If I install 4 x 1mb sticks I get a sad mac (which is understandable). I sadly don't have an oscilloscope so I have no way to check what the output is on SIZ0/SIZ1, or, if it is even those two pins I should be focusing on.

Any help would be more than appreciated as I am really stuck with this one!

 

[Byrd]

Why do you have 256K sticks that are presumably too slow for the SE/30? Can you try more modern modules and clean the slots, connectors and make sure the clips function OK

 

[JYewman]

So I've tried 4MB sticks in Bank 1 and 1MB sticks in Bank 2 and I System 7 reports 2MB of RAM installed, I've checked all of the sticks seperately and they are all working.

 

[imactheknife]

So I've tried 4MB sticks in Bank 1 and 1MB sticks in Bank 2 and I System 7 reports 2MB of RAM installed, I've checked all of the sticks seperately and they are all working.

Have you tried mode 32 and switch it on, restart and see what it says? Weird issue

 

[mikes-macs]

I'd try each set alone in bank A to see if each set at the very least works separately. Then follow this chart.

Memory Upgrades: Mac SE/30 | Low End Mac

 

[JYewman]

Small update, which is throwing more questions, I now have 4x1mb sticks installed in Bank A, but the SE/30 only reports 1MB installed

 

[mikes-macs]

Can you send pictures of the 1 MB SIMMs you're using?

 

[JYewman]

It's this https://www.ebay.co.uk/itm/175562636662 (4x 1MB 30-Pin 80ns Non-Parity FPM Memory SIMMs 4MB Apple Macintosh SE Plus II)

What I find really strange is that when I put 8 sticks of 1MB ram in, I get (large horrizontal) jailbars. When I put 4 in bank A, the system just reports 1MB installed (when I have 4MB). I feel like this has to be either a logic board or chip issue, but I don't know where to start

 

[imactheknife]

It's this https://www.ebay.co.uk/itm/175562636662 (4x 1MB 30-Pin 80ns Non-Parity FPM Memory SIMMs 4MB Apple Macintosh SE Plus II)

What I find really strange is that when I put 8 sticks of 1MB ram in, I get (large horrizontal) jailbars. When I put 4 in bank A, the system just reports 1MB installed (when I have 4MB). I feel like this has to be either a logic board or chip issue, but I don't know where to start

Sounds like possibly a broken trace. How are the simm holders themselves, are the little tabs plastic / broken, or the metal ones?

 

[JYewman]

Sounds like possibly a broken trace. How are the simm holders themselves, are the little tabs plastic / broken, or the metal ones?

I've just ordered some new SIMM sockets as well as replacements for RP1 and UD1, I can't fund any broken traces on the board. (the socket didn't appear to be damaged, but I'm going to replace them anyway). I'm not sure where to really start the hunt for a broken trace.