[joanou]

It's just my experience, I have no formal studies to back it up...

In my multithreaded java application, turning off HT improved performance 100%. Granted, it was one of the early HT implementations wit ha single core, but I still always turn it off in my BIOS.

I tend to prefer AMD over Intel because you get more MIPS/$ and less heat.

[albertcardona]

My java experience is in the opposite direction: using HT enhances performance (but by no means by 100%).

That, with an Intel 5500 (2 quadcores, "16" cores total when using hyperthreading).

[JF-AMD]

I think this helps underscore my point. Sometimes you get performance, sometimes you don't.

I used to work for a major OEM that sold Intel systems. One of the biggest problems was that SQL Server, for instance, ran slower with HT when you had more than 4 threads.

But customers never thought to turn it off because they assumed it was a "performance feature." If it was pitched as a "sometimes" performance feature, then people might be inclined to turn it off to check performance.

If I had a dollar for every customer I had to have that discussion with, I could have bought myself a server.