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Graphics performance and 64 bit OS
cK-Gunslinger wrote:
That's *exactly* what I just said. *If* the code has been recompiled to take advantage of the new 64-bit features, it will perform better; otherwise, not. A 64-bit CPU gives you the ability to use 64-bit memory address, allowing you to have a *lot* more addressable memory that 32-bit (which are 'limited' to ~4GB). Also, the registers are 64-bit, allowing you do perform 64-bit calculations in a single step, as opposed to doing them twice with 2 32-bit numbers. That's it. That's all that's required for a CPU to be '64-bit'. If your applications use a lot of 64-bit number/integers (most do not), then you might see some speedup, Otherwise, not. Simple. 64-bit = 'more memory, larger native numbers' 64-bit != 'inherently faster performance' But like I said before, all the new 64-bit CPUs include numerous other architectural enhancements that will outperform current 32-bit CPUs, so your apps *will probably* perform better on an Opteron than your current p4, but *not* because the Opteron is 64-bit, but rather in spite of it. That's a nice opinion, now, do you have any examples using real-world processors and real-world code to support it? What you claim to be saying and what you are actually saying seem to be more than a little at variance. If the advantages you cite are the only ones that a 64-bit processor provides then why does 64-bit Linux run so much faster than 32-bit Linux on the same hardware? J. Clarke wrote: cK-Gunslinger wrote: All things being equal, a 64-bit machine (CPU + OS) will typically be *slower* than a 32-bit machine. Now, all things are *never* equal and the current line-up of 64-bit CPUs (AMD64, Opteron, etc) have many hardware enhancements (extra registers, larger caches, faster memory interconnects, etc) that will increase overall performance. That being said, if you own a 64-bit CPU and are running in 32-bit mode, will you get better performance simply by installing WindowsXP-64 and some 64-bit drivers? Possibly, but only if the OS/drivers have been tweaked to take advantage of the CPU/chipset's new features. The general "64-bit-ness" of the software does not make anything faster over 32-bit. I'd be interested in knowing on what you base this conclusion. FWIW, with the Opterons Linux shows a marked performance improvement when recompiled as 64-bit code. -- --John Reply to jclarke at ae tee tee global dot net (was jclarke at eye bee em dot net) |
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*sigh* One more time, then I give up:
---- FROM: http://www.osnews.com/story.php?news_id=5768 "So while the tests I ran were on only a few applications and in limited ways, the results seem to show that indeed 64-bits do generally run slower. However, there are there are a few issues to consider." ---- FROM: http://arstechnica.com/cpu/03q1/x86-64/x86-64-1.html "...the only kind of performance increase that you can expect from a straight 64-bit port is whatever additional performance you get from having more memory available. As I said earlier, 64-bitness, by itself, doesn't really improve performance for anything but the rare 64-bit integer application. In the case of x86-64, it's the added registers and other changes that actually account for better performance on normal apps like games." ---- I'm not exactly just pulling random opinions out of my ass here. I have worked for several years in the software industry and have designed and run code for 8-, 16-, 32-, and 64-bit processors. The only statement I'm trying to make, which I've pointed out with each post to this thread, is that "64-bit does not mean inherently faster performance." You even seem to support my statement, with your argument of "... then why does 64-bit Linux run so much faster than 32-bit Linux on the same hardware?" The answer is obvious and was addressed in my previous post with the second statement: "*If* the code has been recompiled to take advantage of the new 64-bit features, it will perform better; otherwise, not." The 32-bit Linux code running on Athlon64 architecture cannot "see" the extra registers, and cannot therefore use them in anyway. Only by recompiling the code with the 64-bit flag can you 'force' the code to recognize the extra hardware and utilize it. I fail to see the "variance" in my claims and I am sorry that I cannot be anymore clear or straightforward with "my nice opinions." J. Clarke wrote: cK-Gunslinger wrote: That's *exactly* what I just said. *If* the code has been recompiled to take advantage of the new 64-bit features, it will perform better; otherwise, not. A 64-bit CPU gives you the ability to use 64-bit memory address, allowing you to have a *lot* more addressable memory that 32-bit (which are 'limited' to ~4GB). Also, the registers are 64-bit, allowing you do perform 64-bit calculations in a single step, as opposed to doing them twice with 2 32-bit numbers. That's it. That's all that's required for a CPU to be '64-bit'. If your applications use a lot of 64-bit number/integers (most do not), then you might see some speedup, Otherwise, not. Simple. 64-bit = 'more memory, larger native numbers' 64-bit != 'inherently faster performance' But like I said before, all the new 64-bit CPUs include numerous other architectural enhancements that will outperform current 32-bit CPUs, so your apps *will probably* perform better on an Opteron than your current p4, but *not* because the Opteron is 64-bit, but rather in spite of it. That's a nice opinion, now, do you have any examples using real-world processors and real-world code to support it? What you claim to be saying and what you are actually saying seem to be more than a little at variance. If the advantages you cite are the only ones that a 64-bit processor provides then why does 64-bit Linux run so much faster than 32-bit Linux on the same hardware? J. Clarke wrote: cK-Gunslinger wrote: All things being equal, a 64-bit machine (CPU + OS) will typically be *slower* than a 32-bit machine. Now, all things are *never* equal and the current line-up of 64-bit CPUs (AMD64, Opteron, etc) have many hardware enhancements (extra registers, larger caches, faster memory interconnects, etc) that will increase overall performance. That being said, if you own a 64-bit CPU and are running in 32-bit mode, will you get better performance simply by installing WindowsXP-64 and some 64-bit drivers? Possibly, but only if the OS/drivers have been tweaked to take advantage of the CPU/chipset's new features. The general "64-bit-ness" of the software does not make anything faster over 32-bit. I'd be interested in knowing on what you base this conclusion. FWIW, with the Opterons Linux shows a marked performance improvement when recompiled as 64-bit code. |
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