Date: Thu, 19 Apr 2001 11:23:56 -0700 From: "Charles Burns" <burnscharlesn@hotmail.com> To: jgowdy@home.com, vince@oahu.WURLDLINK.NET Cc: lplist@closedsrc.org, kris@obsecurity.org, mwlist@lanfear.com, freebsd@sysmach.com?, questions@FreeBSD.ORG Subject: Re: the AMD factor in FreeBSD Message-ID: <F180lDe6l6MMDBfTPQW00002e1d@hotmail.com>
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> > > The only significant performance advantage that the Pentium 3 has over
>the
> > > Athlon is that its l2 cache memory is _much_ faster than that of the
>Athlon.
>
>Could you explain this ? If you're comparing Thunderbirds to Coppermines,
>I
>didn't think that was the case.
Yes, I was comparing Coppermines with Thunderbirds. This is one of the
reasons that the P3e is often very close to as fast as the Athlon at the
same speed. Quick chart:
Athlon T-bird P3e
L1 cache 128K 32k
L2 cache 256K 256k
Total usable cache* 384K 256K
L2 cache clockspeed** CPU core clock CPU core clock
L2 cache BUS WIDTH** 64-bit 256-bit
L2 bandwidth @ 1GHz 8GB/sec 32GB/sec
*The P3 keeps a copy of L1 cache in the L2 cache, reducing the effective
usable cache memory.
**The first P3's had a 64-bit L2 cache running at 1/2 core clockspeed. The
first Athlons had a 64-bit L2 cache running from 1/2 to 2/5 core clockspeed,
depending on the speed of the Athlon. These were the Athlon "classics" as
opposed to the "Thunderbirds". Both the original P3 and the original Athlon
had 512K of L2 cache (twice as much), but this was too expensive to
impliment when the moved the cache to the CPU core itself, so they
eliminated some of it. The P3 Xeons have up to 4 megs of L2 cache.
>In business applications benchmarks the Athlon always stomps the P3.
I have seen this myself on systems that I have tested (even with the
slightly better Intel chipsets)
>If I remember correctly, depending on the type the best SDRAM gets about
>800
>megs/sec. DDR SDRAM comes in two flavors, 1.6 gigs/sec and 2.1gigs/sec.
Yep, the bandwidth can be calculated with the simple equation:
[(Bus width)*(memory clock speed)*(1 if regular RAM, 2 if DDR RAM)] /
(8*1024*1024) = MB/sec
Or something like that.
There are other things to consider like CAS latency, CAS-to-RAS latency and
other latencies which I can't remember at the moment and the chipset and
stuff. DDR is, as you said, certainly much faster overall.
Please let me know if I screwed anything up. ;-)
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