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More than 2GB of system memory

16 January, 2005 in Memory

This isn't a problem most of you will have soon. However, because the possibility exists that the Sager NP9860 will support more than 2GB of system memory (Sager hasn't taken a stand one way or another on this issue yet), we feel like the issue should be addressed. Also, please understand that we've never tested this scenario -- it's still theoretical.

If you put 4GB RAM into a Windows XP machine, when you boot to XP, you'll see something less than that in the System Properties - probably in the neighborhood of 3-3.5 GB. Windows reserves a good chunk of memory addressing for other system resources, such as the AGP/PCI devices.

Here is where it gets trickier. The default setup is that XP has no more than 2GB of memory addressing available in "user space" (applications/games). The other 2GB is reserved for the OS itself. There is a flag described in the links below called /3GB that can be entered into boot.ini on XP Pro, which will change the allocation to 3GB for user space and 1GB for the OS. The caveat to doing this is that the software has to be written specifically for this flag (most is not), and there can be problems that appear due to enabling this option.

My opinion 2GB is the "sweet spot" of maximum memory for most 32-bit Windows users. It is possible that 3GB would be worthwhile, but you'd need to check with your software vendors. I personally wouldn't get 4GB of memory on a 32-bit system because the benefit is probably next to nothing. Keep in mind that 64-bit Windows XP increases the maximum memory to 16GB, and Intel has scheduled a 64-bit Intel Pentium 4 "Prescott" processor for release within the next few months.

Here are some links for more in-depth reading:
http://www.hp.com/workstations/segments/mcad/dassault/windows/
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx
http://support.microsoft.com/kb/291988