Messages in this thread | | | Date | Fri, 20 Aug 1999 11:25:27 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [bigmem-patch] 4GB with Linux on IA32 |
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On Fri, 20 Aug 1999, Thierry Vignaud wrote: > > Yes, but we do can use 24:32 referencse (as
Nope.
That's pure Intel propaganda, and has absolutely no basis in reality.
There's a 13:32 bit address space, with the 13 bits coming from the segment registers. True.
However, that does NOT give you 45 bits of addressing, however much Intel tried to claim that in early literature. The 13:32 address is mapped onto a plain linear 32-bit address space, and that's all it gives you.
[ In theory, you can play games with the present bit in the segments to make it appear like more, but in practice that is basically useless too, don't even bother mentioning it ]
You can make the 36 physical bits available to software the same way people used to do expansion memory on a 286 - by having a window and having software change that window. Some databases would be happy with that. But I much prefer just letting processes have their 3GB worth of address space, and being able to map in the occasional big page when really needed.
Or, actually, I'd much prefer a sane architecture that doesn't continually try to reinvent the bad idea of memory windows.
Linus
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