I currently have an Opteron 170 in a Asus A8N-SLI Deluxe. I tried to install 3 gigs of ram but the system only sees 2.5. So I just am running on 2 now. My question is... is it the OS or the mobo that is limiting this? I've read that 32bit OS's limit the ram and that I'd need a 64bit OS.... any truth to that?
I am building a new system with a ASUS P5W DH DELUXE and an Intel Core 2 Quad Q6600. Will I run into the same problem?
You may have defective RAM, or you may be running into the "4GB limit". Briefly, the issue is that there are only 4GB of possible 32-bit memory addresses. Since hardware takes up some of these addresses, from the top down (with the more boards & devices you have, the more addresses are taken up), RAM can only use the addresses that are left, which can vary from less than 3GB up to about 3.5GB. To use 4GB or more of RAM, you need:
1) A "64-bit" CPU; current and recent Intel and AMD consumer CPUs have this capability.
2) A motherboard chipset that can address 8GB or more of RAM.
3) A motherboard BIOS that includes a "memory remapping" function.
4) 64-bit Windows XP or 64-bit Windows Vista or another OS that can directly address RAM above the 4GB mark.