A single process will go faster with HT than without. HT compensates for an inherent P4 performance problem. Windows happens to utilize HT by making things as if there were two processors, shoving simultaneously running processes into little gaps in the pipeline (I forgot what causes these gaps to occur, but either way processor power that could have been used is instead wasted) where without HT those gaps would simply not be used and be wasted use of processor capability.
So, with Windows 2K/XP, let's say we got 1 QMD running on a P4 w/HT. It is using 100% minus the little pipeline gaps that occur here and there. The reason it will run faster however, is because other stuff that's running, even if it is using very little in terms of CPU, will be filling those gaps instead of interfering with the QMD, or the QMD will be filling some, so there's less "this program or that program" and a little more "both at the same time." However, those pipeline gaps only account for several percent performance loss in total (at most) I think, so it isn't anything close to being like 2 CPUs.
Running two QMDs at once on a HT P4 can yield a worthy extra PPD, in my case around 20. However, if other programs are running, like say download/upload stuff, virus scans, or anything that uses a few percent or more CPU, running two will more likely hurt production than help, or just not really help. This is because those other processes are already vying for the pipeline gaps that HT allows to be utilized, thus negating any possible production increase from the second QMD instance
So only run two QMDs if you're running nothing else. AND you have ample dual channel RAM capacity
Atleast that's my understanding of it (very crude understanding it is!)
