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Does anyone have any logical explaination why the same database SELECT query would run much faster on a Inten XEON W3503 than an AMD Opteron 2425 HE (six core) processor? Even when there are only logical reads (reads to cache). Do the AMD processors run on a much slower bus? Does anyone have any idea?

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Are they on the same machine ? Do they have the exact same hardware ? Do the 2 systems have the same databse with the same contents and same indexes and same hard drives ? Without these info, its impossible to say. –  Sathya Sep 2 '10 at 15:12
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1 Answer 1

With pretty much any SQL database, if you just have the one process running your bottleneck is disk I/O and NOT cpu cycles.

I think if you check the specs on the machine you will find one of the following:

  • There was query caching in the faster one
  • There were other processes running in the slower one
  • The hard drives were different
  • The indexes were different
  • There were flags set differently on the server itself

There are so many configuration options that affect the speed of SQL Server, it's almost impossible to compare apples to apples unless you copy EVERYTHING between machines.

EDIT

Found two links in MS KB regarding issues with AMD processors (one specifically with the opteron):

Link One

Link Two

Both are related to the time stamping function.

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Thank you for your answer. The thing is, I have copied everyting between the machines. And on both queries, all data where fetched from the cache. This is easy to see by turning STATISTICS IO ON. The hard drives are different indeed, but since all data was fetched from cache on both machines, I don't see that hard drive performance would matter? The indexes is also the same on both machines (since the database on the first machine is a replica from the other machine). The slower one also had LESS processes running. This all is why this is so baffling to me. –  Clean Sep 2 '10 at 15:20
    
Ram is the same as well? How long is the query taking? Have you checked execution plans on both to be sure they are the same as well? –  JNK Sep 2 '10 at 15:23
    
RAM is more on the slower machine, 8GB, in camparison to the faster machine that only has 4 GB. I havent checked the execution plans... –  Clean Sep 2 '10 at 15:27
    
Also I found two links that may help. It could be AMD issue. See edited response. –  JNK Sep 2 '10 at 15:31
    
Very interesting. Especially since the server is running Windows Server 2003. Thanx alot!! –  Clean Sep 2 '10 at 15:39
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