4GB RAM recongized as 3GB

decrement · Posted: Thu Nov 04, 2004 5:30 pm Post subject: 4GB RAM recongized as 3GB

hi,
I installed gentoo, kernel 2.9.1, on a dual-xenon Fujjitsu-Siemens Celsius R630 machine with 4GB ram.
If I turn on the 4GB option in the High Memory Support section of the kernel configuration, I only have 3GB displayed in /proc/meminfo after booting.
However, if I switch on the 64GB option I see all 4GB.
this is fine, but I'm still wondering why the 4GB option doesn't work and if switching on PAE (64GB switch) has an impact on the performance?
Is it possible that the memory got stuck into the slots in a non-optimal way?

cheers

matthias

TobySmurf · Posted: Fri Nov 05, 2004 1:19 am Post subject:

I was under the impression that the 4GB option reserved the top GB. Generally if the machine has more than 2GB of RAM I enable PAE. Wise or not, it seems to work very well and made for a no-hassle upgrade when we bumped a couple systems to 16GB...