A couple of weeks ago we upgraded one of our enterprise systems to a clustered environment using Dell Hardware with 2 physical CPUS, 6 Core Hyperthreaded, showing 24 available CPUs in task manager, add in 32gb of memory and still stay under 10k. These were great boxes for the application a document storage retrieval system.
After windows was installed and we started on the SQL2005 initial install the setup would just fail and not report any usable error. What had started as a fairly simple upgrade turned into a nightmare.
After several attempts and several hours of scouring the web our systems guy found an article about SQL2005 not installing on a server where the cores were not divisible by 4. Who would have thought that MS would have been so short sighted, or that the error message would not have given some indication.
Once the system team modified the server to only show a single CPU the install went smooth and after applying SP2 all 24 processors put back into the pool.
Since this upgrade the server is running at under 10 percent CPU usage and very seldom has any type of wait condition.
Hope this helps someone else avoid a headache.