[Gllug] Chipsets and main memory caching

[Mike Brodbelt]

Hi,

I've got a machine which has 2Gb of RAM installed, and runs an Intel
440GX chipset. When I copile a kernel without HIGHMEM, the machine runs
fine (but obviously does not access all the memory), with HIGHMEM on, it
crawls like a dog.

I'm suspecting that this may be due to the motherboard not caching the
entire 2Gb or RAM, but I'm not sure how I can be sure. Is the amount of
main memory cached a limitation of the chipset, and thus the same for
all boards based on the 440GX, or is it a limitation built in by the
motherboard designers?

Either way, is there any hard and fast way to confirm or deny the
theory? Alternatively, does anyone know any other reason why simply
turning HIGHMEM on (this is the 4Gb extension, not the 64Gb PAE
stuff)would slow the machine down by a factor of 10-20?

Mike.




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