Re: [PERFORM] Status of Opteron vs Xeon

2005-10-07 Thread Merlin Moncure
 What's the current status of how much faster the Opteron is compared
to
 the
 Xeons?  I know the Opterons used to be close to 2x faster, but is that
 still
 the case?  I understand much work has been done to reduce the contect
 switching storms on the Xeon architecture, is this correct?

Up until two days ago (Oct 5) Intel has had no answer for AMD's dual
core offerings...unfortunately this has allowed AMD to charge top dollar
for dual core Opterons.  The Intel dual core solution on the P4 side
hasn't been very impressive particularly with regard to thermals.

My 90nm athlon 3000 at home runs very cool...if I underclock it a bit I
can actually turn off the cooling fan :).

IMO, right now it's AMD all the way, but if you are planning a big
purchase, it might be smart to wait a couple of months for the big price
realignment as Intel's dual xeons hit the retail channel.

Merlin


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Re: [PERFORM] Status of Opteron vs Xeon

2005-10-07 Thread Chris Browne
[EMAIL PROTECTED] (Jeff Frost) writes:
 What's the current status of how much faster the Opteron is compared
 to the Xeons?  I know the Opterons used to be close to 2x faster,
 but is that still the case?  I understand much work has been done to
 reduce the contect switching storms on the Xeon architecture, is
 this correct?

Work has gone into 8.1 to try to help with the context switch storms;
that doesn't affect previous versions.

Furthermore, it does not do anything to address the consideration that
memory access on Opterons seem to be intrinsically faster than on Xeon
due to differences in the memory bus architecture.  

The only evident ways to address that are:
 a) For Intel to deploy chips with better memory buses;
 b) For Intel to convince people to deploy compilers that 
optimize badly on AMD to make Intel chips look better...
-- 
(format nil [EMAIL PROTECTED] cbbrowne ntlug.org)
http://cbbrowne.com/info/lsf.html
A mathematician is a machine for converting caffeine into theorems.

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Re: [PERFORM] Status of Opteron vs Xeon

2005-10-07 Thread Tom Lane
Chris Browne [EMAIL PROTECTED] writes:
 [EMAIL PROTECTED] (Jeff Frost) writes:
 What's the current status of how much faster the Opteron is compared
 to the Xeons?  I know the Opterons used to be close to 2x faster,
 but is that still the case?  I understand much work has been done to
 reduce the contect switching storms on the Xeon architecture, is
 this correct?

 Work has gone into 8.1 to try to help with the context switch storms;
 that doesn't affect previous versions.

Also note that we've found that the current coding of the TAS macro
seems to be very bad for at least some Opterons --- they do much better
if the pre-test cmpb is removed.  But this is not true for all x86_64
chips.  We still have an open issue about what to do about this.

regards, tom lane

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