The Windows 32-bit kernel is technically capable of using over 4GB of system memory using technology called Physical Address Extensions (PAE). However, Microsoft only exposes this capability in Server versions of the operating system, Enterprise edition or greater. On the client side, Windows XP prior to SP2 could technically use it as well--MS apparently didn't feel compelled to artificially limit it at that time given how rare >4GB of memory was back in those days. However, beginning with SP2, there's no longer any way to make memory over 4GB accessible to the system or to user applications in XP, Vista, or Win7 x86 editions. 64-bit versions of Windows do not have this limitation--Win7 Professional x64 and above support up to 192GB of memory.
Also worth noting is that even with 4GB, by default, Windows will split this into 2GB of user memory and 2GB of kernel memory. You can use 4GT (/3gb switch in boot.ini) to modify this split to 3/1, but that can introduce its own (rare) issues with poorly written drivers/software, and still doesn't modify the per-process 2GB memory limit unless your memory-intensive applications are compiled with LARGE_ADDRESS_AWARE (also rare). In short, there's rarely significant benefit in putting 4GB in a box with a 32-bit client Windows edition. I'll forego my predictable rant on the archaic nature of XP and relative virtues of newer versions with principle development occurring within the last decade. :) > -----Original Message----- > From: [email protected] [mailto:hardware- > [email protected]] On Behalf Of Veech > Sent: Monday, November 28, 2011 12:50 AM > To: [email protected] > Subject: [H] RAM Upgrade Question > > I have a 5-year old PC that is humming along just fine using XP SP3. The > board is an EVGA nForce 680i which NewEgg says will support up to 8GB > RAM: > http://www.newegg.com/Product/Product.aspx?Item=N82E16813188013 > however I > have always thought that XP will only "see" 4G RAM> Is this true or will my > board actually see the 8GB RAM with XP SP3? I doubt it will, but just > wanted to throw it out there, see what you guys think. > > Currently I have 2 x 1GB DDR2-800 RAM Patriot brand. There are two more > DIMM slots available. Should I toss the 5-yr old sticks and get 2 x 2GB RAM > or just add 2 more 1GB sticks? RAM is cheap enough now that in this case > the cost isn't a major issue. > > thanks! > >
