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Subject: Re: A challenge! (CPU vs CPU)

Author: Jeremiah Penery

Date: 18:37:37 05/07/02

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On May 07, 2002 at 12:16:30, Aaron Gordon wrote:

>Sisoft sandra is fairly accurate when it comes to memory bandwidth. It's
>basically a souped up STREAM benchmark. Also, I notice a very large difference
>between 2.0gb/s and 2.4gb/s. This is 20%. In many applications that are memory
>intensive this gives a MUCH needed boost.

My argument was that the Sandra memory bandwidth test doesn't reflect any kind
of real-world performance.  I'm sure it's accurate as far as raw bandwidth,
under specific conditions.  It comes very close to the theoretical peak
bandwidth, in fact - which is why I don't think it's completely realistic; very
few applications will saturate the bus like that.

>Also, about running 166/200fsb synchronous. Like I said.. the 8k3a+ and other
>similar boards have 1/5, 1/6 PCI multipliers and similar AGP multipliers to keep
>everything within spec while keeping the bus and ram at 166 or 200MHz(333 &

I was talking about running the CPU bus at the normal 133MHz and running the
memory at 166MHz (333 DDR) - _a_synchronous operation - it usually doesn't
produce much speedup, because the processor bus (still at 133MHz) is already
saturated, no matter if the memory bus is putting out 20GB/s.

>400DDR). Thats why I said you can just grab the board & slap in the appropriate
>memory and you're good to go. If you are at 133fsb(DDR) then ~2.0gb/s is about
>all you're going to get, the theoretical max would be 2.1gb/s.

Yep.

>About the Quake3 benchmark, yes, optimization can overcome that gap quite
>easily. Get Quake3 and run the tests (even at 133fsb w/ the tweaks you have
>now). I guarantee with a similar video card you will get (easily) %20 more fps
>than the AthlonXP on the page of a similar clock speed. No if's and's or but's
>about it. Use my DLL's and get ANOTHER 20% :)

As I said, I'm not completely interested in Quake3 benchmarks, but maybe I'll
give it a try sometime.  It's not like it matters once you're over about 100FPS
anyway, because the monitor doesn't refresh so fast.

>Most of the speed increases come from increasing memory bandwidth. With the
>right board & memory you can get some ridiculous scores without having to modify
>anything on the board (just a few settings in the bios, nothing more). Dual
>channel DDR (2x faster than current DDR) is right around the corner.. hopefully

Of course there has been an nForce chipset with dual-channel DDR support for
months. :)

>VIA puts out a decent chipset (like the KT266a & KT333) so we can take advantage
>of such insanity. :)

Via is trying to push DDR400 on us, but I haven't heard much about them doing
any kind of dual-channel thing, which sucks.  IMO, AMD should make their
processors use a 200MHz bus, instead of the 133 they currently use.  Even
without increasing the speed of the processor, the performance would increase
quite a bit, especially with respect to the P4 on bandwidth-intensive
applications.  It's a mystery why they keep everything on the old 133MHz bus -
it has to artificially hold the Athlon's performance down.



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