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 problem. -- Terry To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
