Messages in this thread | | | Date | Wed, 16 Oct 2002 13:46:31 +0200 (MET DST) | From | "Maciej W. Rozycki" <> | Subject | Re: mapping 36 bit physical addresses into 32 bit virtual |
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On 15 Oct 2002, H. Peter Anvin wrote:
> Oh no, the x86 madness is spreading!!!! > > (It's depressing this happening on a MIPS system, which has been 64 > bits since who-knows-when...)
Yep, but the reasons are different -- the embedded people are paranoid on cutting away any possible bit of silicon and, admittedly, they are right, to some extent. Why do they need 36-bit physical addressing in 32-bit cores remains a mystery to me, though, yet the MIPS32 ISA spec permits up to 36 bits (implementation-specific) here. Even more interesting is why an implementation chose mapping of I/O devices there -- it's usually easier for an OS to have them mapped within the low 29-bit address space where they can be accessed bypassing the TLB.
-- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
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