topic Re: Hyperthreading in Operating System - HP-UX

Hyperthreading

Joel Robe — Sun, 15 Aug 2004 02:06:35 GMT

I am trying to find out if the PA 8700 750 mhz cpu is capable of hyperthreading. Is there anywhere where I can find this information or does anyone know? If the PA 8700 is capable of hyperthreading, how do I start it? If the PA8700 isn't capable are there others that will work with our HP9000 rp5470? Thank you for any help you can provide.

Re: Hyperthreading

Hein van den Heuvel — Sun, 15 Aug 2004 14:29:52 GMT

No Hyperthreading in the PA line.
The is the dual-core 8800... better than hyperthreading.

In the IA64 area one could speculate that there will be some hyperthreading (once Intell releases). Best I know the hpux folks are still deciding on how best to make use of that if and when available.
So, way to early for here and now hyperthreading.

Cheers,
Hein (from chicago)

Re: Hyperthreading

rick jones — Mon, 16 Aug 2004 10:16:44 GMT

Indeed, none of the PA-RISC CPUs do hyperthreading. They get much of their performance from out-of-order execution.

Like anything else, hyperthreading is a "Your Mileage May Vary" kind of thing. It can help (possibly) if you have different threads of execution that spend much of their time blocked waiting for a cache miss to be satisfied. If however, they don't block much on cache misses, you don't get that much from hyperthreading, and instead, unless the CPU is designed very well, you can get problems like cache pressure and perhaps TLB thrashing.

Iff you are looking to get more performance out of an application on PA-RISC, I'd probably start with some of the more "traditional" methods such as examining a profile (prospect) and perhaps even looking at the output of "pi" (ftp://ftp.cup.hp.com/dist/networking/tools/) if you think things are 'CPU' bound.

Re: Hyperthreading

Joel Robe — Mon, 16 Aug 2004 16:05:35 GMT

Thank you all for the help. I have the answer I need and will research all of the other great info I received.