Ben Scott wrote: > It's actually not a processor issue.
Well, kinda but not really. It's an architecture limit of 32bit. > The processor can map RAM > around address space that hardware needs, and with PAE, the processor > can map to RAM above 4 GB, too. In Windows XP, Microsoft made the > decision to just cordon off the upper part of the 32-bit virtual > address space, reserving it for kernel, device drivers, and hardware > I/O. Windows Server doesn't have that restriction (neither does > Linux). That statement is vague to the point it's not correct. All 32bit OS's have this limitation, even Windows Server. Certain versions of Windows Server 32bit, as well as 32bit Linux and *BSD that support PAE, are able to fully address and use 4GB (or more) of memory. Now, while XP and Win2003 STD/SBS/WEB also support PAE, it's for other purposes and Microsoft has limited the OS to not be able to address memory outside of the 4GB barrier which it must be able to do if you want to see all 4GB. > One explanation I've read is that a lot of device drivers just > assume addresses are within that space <snip> Only 4GB of address space exists on the 32bit architecture unless your OS supports more *and* supports PAE. RAM isn't the only thing that exists in that address space. Resources for your video card, the BIOS, etc. also need address space *below* the 4GB barrier. PAE enables address space above the 4GB barrier so the memory that wasn't usable below it can then be made available above it. Just say'n. -- Mike Gill ~ Upgrade to Next Generation Antispam/Antivirus with Ninja! ~ ~ <http://www.sunbelt-software.com/SunbeltMessagingNinja.cfm> ~
