On Thu, 17 Mar 2005, Peter W. Morreale wrote:
(I did not see this addressed in the FAQs...)
How much physical memory can the 2.4.26 kernel address in kernel context on x86?
All of it.
What about DMA memory?
All of it, too. The old DMA controller(s) could only address 16 MB because that's all the page-registers allowed. Bus-mastering DMA off the PCI/Bus has no such limitation. Most have DMA controllers that use scatter-lists so RAM doesn't even have to be contiguous, only properly allocated (in pages) and nailed down with no caching.
Local rumor says ~1GB. But this makes little sense given a 32-bit address.
If you are looking for a dynamic buffer in DMA-able RAM, you probably can only use aout 1GB, but that's not how to do DMA.
Where in the source can I learn more about this?
../linux-`uname -r`/mm
Thanks, -PWM
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