[Reece]

Originally Posted by Captain Nemo

From what I have read Reece is correct. I'm no computer expert but from what I have read the switch has nothing to do with how much RAM you have installed, for example you could use the switch on a machine with only 1GB of physical RAM installed. It's all to do with virtual memory which XP 32 bit can have a maximum of 4GB. On a standard setup XP allocates up to 2GB of VM to applications and up to 2 GB to the OS. The 3GB switch gives 3GB to applications and only 1GB to the OS. So theoretically, if some hardware on your machine wants to push the OS side of things beyond that 1GB, problems will arise. Also, some applications don't like the idea of more than 2GB of VM so issues with those may arise. On the other hand if your OS and drivers can live happily within that 1GB then you should be problem free. I suppose the workaround is to have the option at boot up to select the 3GB switch if your going to play SH3 (assuming your video drivers can live within 1GB with the OS) or to go with a standard boot up if you are using hardware or software that is affected by the switch.

Nemo

For more information:

XP 32 can only use a memory address space of 4GB. It then "RESERVES" addresses in that table for loading every little bit and piece in your computer (Devices and so on like a SATA controller... They all need an "address RANGE" to exist in so that the Os can communicate with it) leaving 3.25GB (3402084 in task manager) of RAM free for the system. XP loads up and uses some of that. Typically after XP loads into memory you will have about 2.9GB free. If you have 4GB physically installed that is.

The more RAM on the video card, the less you have free to the OS is the concept because the OS needs to reserve the address space for the RAM on the video card. I have a 512Mb card and I have XP SP3 reporting 3.25GB free. Theory is that if it were 1GB card I would have less reported available to the Os because the addresses for that 1GB will need to be reserved.

If you have a 2GB PC with a 1GB Card and a 32bit XP install. You likely have very little left for the FSX app to run in.

http://www.dansdata.com/askdan00015.htm

"a note about the /3GB, /4GT and /PAE Windows boot.ini switches, too, because they often come up when people are talking about 4Gb-plus Windows PCs. They are all useless to you. You do not want them. /3GB and /4GT are config settings for different versions of Windows that tell the operating system to change the partitioning of the 4Gb 32-bit address space so that applications can use 3Gb and the OS kernel only 1Gb, as opposed to the standard 2Gb-each arrangement. They don't help at all with the 3Gb barrier, and most applications don't even notice them, so desktop users lose kernel memory space (and system performance) for no actual gain at all. The /PAE boot.ini switch, on NT-descended Windows flavours, activates the Physical Address Extension mode that's existed in every PC CPU since the Pentium Pro. PAE can also be enabled by the /NoExecute entry in boot.ini, which turns on support for the NX bit which you probably also don't actually want.