Author: Eugene Nalimov
Date: 14:28:04 08/15/03
Go up one level in this thread
Words "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." in the article are very badly formulated. Yes, later in the article they are explaining what they meant, but at least one reader was left with absolutely wrong impression... Thanks, Eugene On August 15, 2003 at 15:08:36, Dann Corbit wrote: >On August 14, 2003 at 18:36:51, Eugene Nalimov wrote: > >>Martin, >> >>I'd recommend you not to read articles on the web site that published the >>information you quoted. >> >>Once again: IA-64 can natively execute all user-level x86 instructions, though >>on both Itanium1 and Itanium2 they are executed slow. > >Is the article incorrect when it states that x86 instructions are run through a >x86-to-IA-64 decoder, that takes x86 instructions and decodes them into IA-64 >instructions? > >It seems to me that it says that x86 instruction will run on those chips but >very slowly. That is the same thing that you said. > >Why (therefore) should anandtech be avoided? > >>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. >>> >>>http://www.anandtech.com/cpu/showdoc.html?i=1815&p=5 >>> >>> >>>Martin.
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