Author: Vincent Diepeveen
Date: 20:00:40 09/15/01
Go up one level in this thread
On September 15, 2001 at 22:38:45, Robert Hyatt wrote: >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. Well i haven't tested a hammer yet, so we will see, in the meantime try to figure out the speed of 64 bits instructions at the MMX part of the P4 :) > > >> >>> >>>> >>>>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... You are of course right here, but there is a small practical problem: all windows applications will crash. Graphical coordinate system is completely 32 bits oriented. expanding it to 64 bits will give huge problems. No take my word, unless this is another paper processor, it will be 2 processors within 1 processor, because otherwise there is this problem... ...that all windows applications will not compile easily onto it! > > > >>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... It is a very poor compiler for Alpha, MIPS, SPARC etc. The more registers the bigger the problem for GCC. The speed difference on P2 processor was 7.5% in disadvantage of linux. At the P3 it is already more near 11%. The more registers the bigger the problems of gcc! Of course i hope it gets better, but there is little hope! The main thing to realize however is that a new 1.5Ghz clocked processor is not so impressive when there is a 40% slower compiler at it than a commercial equivalent would be! Because all the innovations of the processor then are completely useless in general speaking. Of course with inline assembly and many volunteers to write new inline assembly for you, you will survive with crafty and be probably the only happy exception for this processor, but that's not very encouraging for others to buy it! > > >> >>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... Everyone told me it was possible. I toyed for months. Now i'm not worlds smartest linux user, because all those tens of thousands of commands which you have to memorize i keep forgetting, but all i manage with gcc is to compile it for 32 bits and for linux native! Note that the gcc compiler at the 21164 didn't particularly impress me when compared to the DEC compiler! > > >> >>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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