View Full Version : F8 x86_64 AMD 64x2 memory address range

29th January 2008, 08:49 PM
I have a F8 system with a Gigabyte GA-M57SLI-S4 motherboard, an AMD 64x2 4600, and 4x1 GB OCZ2P8002GK DDR2 6400 ram. Gigabyte's documentation for this board says it will support 16 GB (i.e. 4x4GB) of main memory.

I just upgraded this machine from 2x1 GB. At the first power up after installing the two new sticks, the BIOS reported ~3.2 GB of ram. I reset the motherboard's CMOS, rebooted, and the BIOS then and now reports 4GB (actually, 4095MB). However, after booting into F8, free reports ~3.35 GB and the system monitor reports 3.2GiB. I believe both should be nearer 4GB.

I have read several threads here and elsewhere about memory limits, and it seems universally accepted that 64 bit hardware running a 64 bit kernel have no limit at 3.2GB.

The new memory was installed in a working FC8 machine. Do I need to do some kernel tuning to access the memory?

What do I need to do to have the full 4GB of memory recognized and used?

[phil@frederic ~]$ uname -a
Linux frederic #1 SMP Mon Jan 14 22:07:11 EST 2008 x86_64 x86_64 x86_64 GNU/Linux
[phil@frederic ~]$ free
total used free shared buffers cached
Mem: 3355476 887400 2468076 0 21068 380616
-/+ buffers/cache: 485716 2869760
Swap: 0 0 0
[phil@frederic ~]$


30th January 2008, 10:41 PM
I think I have managed to fix my problem. I think it was a buggy and lying BIOS. Sometimes it would show 4095MB extended memory and sometimes 3327MB depending on its mood. That was BIOS FE for the Gigabyte GA-M57SLI-S4 rev2 (to which I had upgraded for its virtualization support). Updating to BIOS FFC (published 4 Jan 2008) seems to have fixed my memory access problem, and now I can see all of my new memory. Maybe this info will help someone else.