On 8/15/05, Rick Wagner <wagnerric@xxxxxxxxxxxxxxxxxxxxxx> wrote: > Hi, > > I have seen reference to kernel support for up to 32GB on 32 bit x86 > platforms, with supporting hardware (some versions of Xeon?). Yes, the kernel can use up to 64Gb. > Perhaps I used the wrong search terms, but I could not locate much detailed > information on the subject with Google. Specifically, I was told that the > kernel could map the memory virtually, but the I/O sub-system could not > handle physical I/O to address over 32 bits, thus I/O to high memory was done > via bounce buffers (i.e., DMA to low memory, then CPU copy to high). I'm no hardware guru, but I believe it also has to do with devices on the PCI bus not being able to access the high memory. > Can anyone point to some documentation on the large memory implementation I > can use to confirm or refute what I was told? Search for "linux high memory"; first hit is quite extensive: http://kerneltrap.org/node/2450 Klaasjan
