Re: [Lse-tech] Re: maximum possible memory limit ..

From: Gerrit Huizenga (gh@us.ibm.com)
Date: Mon Apr 28 2003 - 13:31:04 EST


On Mon, 28 Apr 2003 10:53:53 PDT, David Mosberger wrote:
> >>>>> On Mon, 28 Apr 2003 19:13:53 +0200, Andi Kleen <ak@suse.de> said:
>
> >> Cool. Sorry to be pestering about the 64-bit limits, but can we
> >> really use 2^64 bytes of memory on ia64/ppc64/x86-64 etc.?
> >> (AFAIK, 64-bit arches don't suffer from a small ZONE_LOWMEM.)
>
> Andi> No. The hardware have far smaller physical limits.
>
> Andi> Current AMD64 CPUs are limited to 40bit physical, 48bit virtal
> Andi> (the virtual limit per process in the current Linux kernel is
> Andi> 39bits)
>
> Andi> Itanium 2 afaik support a bit more 50bits (51 or 52, I forgot)
> Andi> physical, probably more virtual.
>
> Itanium 2 supports all 64 virtual address bits and 50 physical bits
> (in what way is "1024 times more" "a bit more"? ;-).
>
> --david

0x400 is just one more bit, albeit slid around a byte or two. ;)

gerrit
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