johnklos said:

Hi, m68k users!

I've been using bbraun's djMEMC fix in the NetBSD kernel to support 260 megs in a Quadra 610. However, sometime between last summer and now I've noticed that when I'm booted in to Mac OS 8.1, the Quadra is showing 132 megs whereas it was definitely showing 68 megs in the past. This isn't after warm-restarting from NetBSD or anything like that (I think bbraun mentions or implies that the ROM memory routines run on all boots, so changing-then-rebooting to get more memory isn't an option).

Has anyone else seen 132 megs on a Quadra or Centris 610 without modifications?

Click to expand...

I need to check my notes, but IIRC, the C610 is amongst the machines which sees 1/2 the RAM capacity for SIMM bank sizes above 16 MB.   I'm pretty sure that instead of supporting 13 Row X 13 Col addressing, it only supports 13 X 12 or 12 X 13, which is weird.   Perhaps Rob knows the exact mechanism.

In any case, showing 1/2 the capacity, if you install a pair of 128MB SIMMs you should get a total of 132MB of RAM detected by the OS.

Ordinarily, the specified maximum capacity for the C610 is 68MB (72MB on the 8MB model).  And if you install a pair of 64MB SIMMs, you'll still just get 68MB.   But a pair of 128MB SIMMs should take you to 132MB.  I don't know if it's reliable in that configuration.   If the memory controller is just doing 13 X 12 addressing, then it should work fine.

The later Q660AV and Q840AV and the Nubus PowerMacs (except the 6100) only see 1/4 of the capacity of large SIMMs (seem to be limited to 12 X 12 addressing) so installing 128MB SIMMs in those later models gains one nothing over just installing a 32 MB SIMM.