Author: Robert Hyatt
Date: 19:38:45 09/15/01
Go up one level in this thread
On September 15, 2001 at 19:59:15, Vincent Diepeveen wrote: >On September 14, 2001 at 17:51:46, Robert Hyatt wrote: > >>On September 14, 2001 at 15:54:40, K. Burcham wrote: >> >>> >>> >>>below is part of an artical that i read on the net. >>>i know you could get real technical about 64 bit. not necessary >>>but here is my question. >>>if we have two processors both 1500 mhz. both same brand. but "a" >>> has 32 bit 1500 mhz with 32 bit program. >>>"b" has 64 bit 1500 mhz with 64 bit program. >>> >>>how would a kns benchtest compare with these two examples? >>>so if in example "a" the kns benchtest was 1200 kns for 32 bit, >>> what would the 64 bit do in a similiar benchtest. >>> >>> >> >>_if_ the 64 bit program really uses 64 bit integers, then it will be faster. >>Because the 64 bit processor is doing one 64 bit operation every cycle, while >>the 32 bit processor will do only one 32 bit operation every cycle. The >>requirement is that the program really has to use 64 bit stuff. But if it does, >>a 64 bit machine is potentially twice as fast as a 32 bit machine... >>That is the driving force behind 64 bit development, in fact. > >But in reality the 32 bit operations go at a rate of nearly 2 a cycle and >on paper can get 3 a cycle versus the 64 bits we must wait and see how >many a cycle can be done :) Vincent, please study some of the spec sheets first. The 21264 already executes _four_ instructions per clock cycle. That is why the thing has a 256-bit wide data bus to memory. > >> >>> >>>Hammer processors, sometimes referred to as "K8," will first be produced on an >>>advanced 0.13 micron SOI process out of AMD's Dresden megafab. Unlike Intel's >>>Itanium, Hammer chips will provide uncompromised performance on legacy 32-bit >>>applications as well as open up the 64-bit computing "new frontier." In fact, >>>Hammers are expected to be the fastest chips in the world at running 32-bit x86 >>>code, while seriously challenging the fastest 64-bit processors on 64-bit code. >>> >> >> >>It is unlikely they will do both well. But there are exceptions. IE if you >>use single-precision floats vs double-precision floats on an IBM RS6000, you >>will find _zero_ speed difference. Because the RS6000 does all FP operations >>in 64 bits. So using 32 bit numbers is somewhat slower than on a real 32 bit >>machine that pumps less data around. > >I doubt they will do this, because 'int' should go to 32 bits integers. Nothing in the ANSI standard says this. Which is unfortunate, but it is a way of life in the ANSI world... the standard that "isn't", really... >It would mean they need a very special compiler to run normal executables >on this processor in short. Not particularly. GCC already compiles for 64 bit machines. Alpha, MIPS, SPARC, etc... > >I think this is why the IA64 hasn't reached me yet, because i need to >especially compile for it. > >Now that's still pretty simple as i have a cross compiler at home, >so we can generate IA64 bits native code at a 32 bits machine (of course >not run it). > >However, i doubt they will be able to do that with GCC soon. >I've toyed quite some with gcc and making a cross compiler >is pretty hard! It is already done. In fact, linux for IA64 is fully functional. Which means that GCC had to be finished first... > >I will of course not buy hammer but cross compiling an executable for it >is no problem if i can get a compiler that can produce a hammer native >executable. > >Knowing the problems of GCC just a little bit >i doubt this will happen soon! > >Note i never managed to create at my own PC-linux machine a gcc version >which could create executables for the alpha (with linux of course onboard). > I have one on my alpha at the office. Works fine... using the same one I use on my quad xeon in fact... >So that's why i still till today do not have hard numbers on how fast/slow >a 21264 for me is! > >>>The first desktop Hammer product, the so-called "Clawhammer," will also be only >>>slightly more expensive to produce than contemporary Athlons making 64-bit >>>processing a real option for the masses in the near future. >>> >>>kburcham
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