Steve O'Hara-Smith wrote:
> On Mon, 22 Apr 2002 06:04:34 -0700
> Terry Lambert <[EMAIL PROTECTED]> wrote:
> TL> FreeBSD doesn't currently support bank selection. Peter was
> TL> working on it, last time I heard. Linux supports it, at an
> TL> incredible performance penalty.
> This inspired an off the wall thought that may be insane. Would
> it be possible (on a >4Gb system) to address 4Gb of RAM and write a driver
> to make the rest appear as a device, which could then be used for a
> preferred or (even neater) first level swap.
Only if you reserved a window for it. Say 1G of KVA, though last
I checked the bank selection granularity wasn't fine enough for
that. Memory in the window can *never* be a target for DMA, and
should *probably* never be used for kernel structures.
If you ever programmed graphics on a TI 99/4A, which has a 4k
visible window onto screen memory, or programmed code on the
Commodore C64 to use the 32K of RAM-under-ROM, or programmed
in DOS or CP/M using Overlays, then you'll be familiar with the
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