Alan, the word "virtual" means "almost real" (my own definition), and in the context of memory, it means using the disk drive as an extension to whatever amount of physical memory may be installed on the motherboard.

Note that the settings I mentioned in #4 relate to the virtual memory (paging file) used by the operating system (Windows).

Such VM allows Windows to "virtually" extend the amount of available RAM by spilling over into the paging file on the disk drive. If Windows lacked that capability, and your program needed more memory space, Windows would either have to tell you that not enough memory is available, or it would have to suspend another application, roll its allocated memory contents to a temporary file on the disk drive, and then give you that memory temporarily. When Windows again decided to turn control back to the other application (so it would not appear to be stalled), it would suspend your application, roll your allocated memory contents out to disk, reallocate the area to the other application, reload the first file back into that area, and finally, give control once again to the other application.

Because this can happen many times per second, all that thrashing slows things down tremendously because accessing data on a disk drive is hundreds of times slower than accessing physical memory. That's why the existence of VM increases performance.

Regarding VM size, no number is sacred, but the general recommendation is to give Windows 1.5 to 2.0 times the amount of physical RAM for its virtual memory, or paging file. If the OP had 4GB or RAM instead of 2GB, I would have suggested following the general recommendation of using 1.5 times that, or 6GB, for the paging file.

You mixed the term "scratch disk" into your question. I assume you mean the VM that Photoshop uses, as defined in the Preferences window. (This VM is available only to Photoshop--it does not share it with Windows.) I understand that Photoshop does things differently, using the scratch areas first, resorting to RAM only when necessary. So, when it comes to scratch disk space, the more the merrier.

Ghost_Nine

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