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Subject: Re: Is Xeon 5000 (Dempsey) with FB-DIMMs faster then Opteron 280 ?

Author: Vincent Diepeveen

Date: 12:26:45 11/08/05

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On November 08, 2005 at 13:17:42, Yar wrote:

>Hello,
>
>Here is review (total 14 pages) of upcoming Intel's Xeon 5000 (Dempsey). Sorry
>its only in german. It seems its faster then Opeteron 280.
>http://www.tecchannel.de/server/hardware/432957/
>
>With best regards,
>
>Yar

It should be a fast cpu that Dempsey. However that Xeon will be there januari
2007 or so and it will have a price of i guess around 5000 euro a cpu in the
quad version, if you can get it for that, as you'll have to buy probably
1000 at a time to get them for around 4500 dollar a piece.

So effectively a quad xeon dual core will be januari 2007 around $40k.

By that time of course a quad opteron quad core is nearly 2 times faster
and exactly 2 times cheaper.

Please note that it's not sure whether the IPC from the intel pentium-m at such
high clockspeeds and dual core will be better than from AMD. I'm counting at it
that it will be a lot slower, because in order to clock pentium-m higher, intel
will need to make the pipeline longer and will probably  move from a 2 cycle L1
to a 3 cycle L1. In which case the processor is similar to the opteron from
chessprogramming viewpoint.

Of course the Xeons have bigger L2 or even L3 caches on chip than AMD. That's
nice for certain applications that are in benchmarks, but in reallife it's not a
huge advantage.

A few MB's is plenty for computerchess at the moment.

On the other hand, could you tell me whether this Xeon has an on die memory
controller or doesn't it have one?

Because *that* matters a lot. Hashtables is a matter of TLB trashing memory
latencies to a big hashtable. With 64 bits cpu's and the clock that keeps
ticking, the RAM sizes will increase too, meaning that the latencies you lose to
TLB trashing (transpositiontable , eval table, not so much pawntable as that'll
be in L2 cache for majority of accesses) are significant.

If intel plans to do that via some sort of chipset off chip, then that is a huge
drawback of this Xeon cpu for databases and chess. At database benchmarks, using
some small database they can get away with a big L2/L3 then, but in real life
there is no escape there. It's just dead slow.

So i do look forward to pentium-m, but the price at which intel usually sells
good cpu's doesn't mean that we will see more quads online.

Vincent




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