Toggle sidebar Toggle sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Blue and White only seeing half of the RAM

Nermal

Nermal

Moderator
Original poster
Staff member
My B&W G3 has been running on 128 MB, so I just bought two 256 MB modules for it (to bring it up to 640 MB). However, the system is seeing each of the new modules as only 128 MB (for a total of 384 MB). I've reseated them and checked the labels, they're definitely 256 MB modules.

Help! 😱
 
The Blue and White G3's memory controller only supports memory of a limited density.

It will only read the first half of the higher density chips.

I believe it works roughly like this:

512MB card (Only sees 256MB)
[32] [32] [32] [32] [32] [32] [32] [32] front
[32] [32] [32] [32] [32] [32] [32] [32] back

high density 256MB card (Only sees 128MB)
[32] [32] [32] [32] [32] [32] [32] [32] front
[ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] back

low density 256MB card (Works)
[16] [16] [16] [16] [16] [16] [16] [16] front
[16] [16] [16] [16] [16] [16] [16] [16] back

high density 128MB card (Works)
[16] [16] [16] [16] [16] [16] [16] [16] front
[ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] back

low density 128MB card (Works)
[8] [8] [8] [8] [8] [8] [8] [8] front
[8] [8] [8] [8] [8] [8] [8] [8] back

Macsales.com and DealRAM.com would be good places to look for compatible modules.
 
Ugh. I've just emailed the place I bought it from to see whether they can get me double-sided modules. In the meantime it looks like I'll have to find someone to sell this single-sided stuff to.
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back