I have seen this term used a few times and wondered if someone could explain to me exactly what it is and what the difference is from normal.

Thanks in advance for answering a newb question...

HT or HyperThreading Technology - easiest way to put it. One processor acting as two. Allowing applications and the OS to have two threads(or processes) done in each cycle.
Does not mean that a 3.0GHZ P4 w/ HT with out perform 2- pIII 1.5GHZ though. Lots of other factors come into play. Cache size being a very important one. Also two _physical_ CPUs will handle the load better than "_one_ acting as two"

If you want more search on google... heres one thing that might help. http://searchwin2000.techtarget.com/sDefinition/0,,sid1_gci828854,00.html

so if I have the choice between a Dual Xeon 2.8 and a P4 3.0Ghz w/HT I take the Xeon correct?

Yes. Most likely that P4 is the older generation with a 512 cache. (not even sure if the 3.0 comes with the larger cache of today or not...have to check) But most likely those Xeons has a larger cache...not to mention they are a lot better.

Defintly as HT will not give you near the 200% performance as a Dual Box would ( I know really its like 180% but for the sake of argument)

Rus

Dual Xeons at that speed should have hyperthreading too, so that will be two physical CPUs, showing up as 4.

- Matt

Don't even think about it, go for the dual xeon one, you will be impressed with the power it delivers compared against the P43.0HT.

I love hyperthreading and not just because the idea was invented inside my department at the UW. Check out the wikipedia defintion of HT at http://en.wikipedia.org/wiki/Hyperthreading

so running dual xeon in HT mode is better than running them as dual CPUs with noht option in lilo.conf ?

some ppl said it might give better performance for loaded mysql boxes, are they wrong?

Sure running dual xeons in HT mode is better than running them as non-ht processors.

It's just a matter of the amount of threads that can be passed to the processor at the same time, and therefore the time it needs to complete the job.

Originally posted by schmeg007
I love hyperthreading and not just because the idea was invented inside my department at the UW. Check out the wikipedia defintion of HT at http://en.wikipedia.org/wiki/Hyperthreading

The UW?

University of Washington Computer Science department is what I was referring to.

EDIT:
No, I didn't get to work on the research project, it was a bit before my time :).

A link to the project: http://www.cs.washington.edu/research/smt/

Originally posted by schmeg007
University of Washington Computer Science department is what I was referring to.

EDIT:
No, I didn't get to work on the research project, it was a bit before my time :).

A link to the project: http://www.cs.washington.edu/research/smt/

Wow that's awesome :)