Q660AV max memory ?

[iPhil64]

Hi all,

I just did a test on my Q660AV. I had two 64 MB 72-pin. SIMM from Keystron in stock and popped them in.
I know max memory is supposed to be 68 MB (ie 4 MB soldered, and 64 MB SIMMs).

To my surprise, the Mac, running 8.1, lists 36 MB RAM with two sticks, 20 MB with one SIMM.

So, the 64 MB SIMMs are recognised as... 16 MB ?

 

[iPhil64]

I checked the pin layout, and PD1 is grounded, PD2 is open, which is normally for 16 MB.
To the best of my knowledge, both should be grounded for 64 MB.... I think I will solder this for a test

 

[iPhil64]

OK... answering to myself, the 660AV is limited to 16 MB per bank.
Apple says that in order to reach 68 MB, you need to use 16 MB RAM chips.... like two 16 MB chip per SIMM. I don't get that. I think Apple documentation has a typo, they talk about 16 Mbits chips, not 16 Mbytes.

The 8 x OKI chips (MD51V65405) on the SIMM are 8 Mb each (4 Mb x 4) for the correct total of 64 MB, but PD2 is not grounded.... why ?

OK my head is exploding, to I'm tired. Anyone would have an idea ?

 

[iPhil64]

Kudos to @max1zzz for waking me up on Discord....

 

[imactheknife]

My 660 shows 70 megs of ram