Author: Bo Persson
Date: 12:02:16 08/17/03
Go up one level in this thread
On August 15, 2003 at 08:41:58, Anthony Cozzie wrote: >On August 14, 2003 at 18:07:17, Martin Andersen wrote: > >>On August 14, 2003 at 17:46:03, Eugene Nalimov wrote: >> >> >>>>>32 bit programs can run on a 64 bit computer. >>>> >>>>Yes, but 32 bit programs will run slowly on a pure 64 bit >>>>computer like Intel Itanium, because the system needs to emulate >>>>32 bit in software. >>> >>>Exactly the other way. On Itanium2 software emulation of x86 is much faster than >>>direct hardware support :-) >>> >>>Thanks, >>>Eugene >>> >> >>You are wrong. >> >>Quote from www.anandtech.com : >> >> >>In the past, Intel had been the ones to extend the x86 ISA (Instruction Set >>Architecture) beyond its 8-bit foundation. But once Intel hit 32-bit and started >>to look towards the future and 64-bit microprocessors, they wanted to rid >>themselves of the somewhat bulky x86 ISA and move towards something much more >>robust - and thus, IA-64 was born. >> >>The IA-64 ISA is significantly better than the x86 ISA in a number of ways, but >>the discussion of IA-64 is beyond the scope of this article as we're here to >>focus on x86. The biggest problem with the IA-64 ISA and thus IA-64 >>microprocessors is the lack of native x86 compatibility, effectively keeping >>IA-64 processors from running over two decades worth of software. Intel >>recognized this and equipped their IA-64 processors (Itanium, Itanium 2, etc…) >>with an x86-to-IA-64 decoder, that takes x86 instructions and decodes them into >>IA-64 instructions. This decoder is not the most efficient decoder nor is it the >>best way to run x86 code (the best way would be to run it natively on an x86 >>processor), and thus the Itanium and Itanium 2 offer quite poor performance >>under x86 applications. > >Just read the whole thing. Although I'm told that the IA64 blows on IA32 code, >so I believe Eugene when he says software emulation is faster than the "native" >support. And that should maybe get us to think twice before stating that the Opteron is so fast, because it *has* hardware support... > >anthony Bo Persson bop2@telia.com¨
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