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Re: Large (8M) cache vs. dual-core CPUs

From: Leigh Dyer <leigh(at)eclinic(dot)com(dot)au>
To: mark(at)mark(dot)mielke(dot)cc
Cc: Scott Marlowe <smarlowe(at)g2switchworks(dot)com>,Bill Moran <wmoran(at)collaborativefusion(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: Large (8M) cache vs. dual-core CPUs
Date: 2006-04-26 01:53:06
Message-ID: 444ED282.6010102@eclinic.com.au (view raw or flat)
Thread:
Lists: pgsql-performance
mark(at)mark(dot)mielke(dot)cc wrote:
> Another benefit of Pentium D over AMD X2, at least until AMD chooses
> to switch, is that Pentium D supports DDR2, whereas AMD only supports
> DDR. There are a lot of technical pros and cons to each - with claims
> from AMD that DDR2 can be slower than DDR - but one claim that isn't
> often made, but that helped me make my choice:
> 
They're switching quite soon though -- within the next month now it 
seems, after moving up their earlier plans to launch in June:

http://www.dailytech.com/article.aspx?newsid=1854

This Anandtech article shows the kind of performance increase we can 
expect with DDR2 on AMD's new socket:

http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2741

The short version is that it's an improvement, but not an enormous one, 
and you need to spend quite a bit of cash on 800Mhz (PC6400) DDR2 sticks 
to see the most benefit. Some brief local (Australian) price comparisons 
show 1GB PC-3200 DDR sticks starting at just over AU$100, with 1GB 
PC2-4200 DDR2 sticks around the same price, though Anandtech's tests 
showed PC2-4200 DDR2 benching generally slower than PC-3200 DDR, 
probably due to the increased latency in DDR2.

Comparing reasonable quality matched pairs of 1GB sticks, PC-3200 DDR 
still seems generally cheaper than PC2-5300 DDR2, though not by a lot, 
and I'm sure the DDR2 will start dropping even further as AMD systems 
start using it in the next month or so.

One thing's for sure though -- Intel's Pentium D prices are remarkably 
low, and at the lower end of the price range AMD has nothing that's even 
remotely competitive in terms of price/performance. The Pentium D 805, 
for instance, with its dual 2.67Ghz cores, costs just AU$180. The X2 
3800+ is a far better chip, but it's also two-and-a-half times the price.

None of this really matters much in the server space though, where 
Opteron's real advantage over Xeon is not its greater raw CPU power, or 
its better dual-core implementation (though both would be hard to 
dispute), but the improved system bandwidth provided by Hypertransport. 
Even with Intel's next-gen CPUs, which look set to address the first two 
points quite well, they still won't have an interconnect technology that 
can really compete with AMD's.

Thanks
Leigh


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