Problem with HT processor

[Dresdenboy]

Originally Posted by mimic

This does not work. Prime95 then runs on CPU 0, but the other program jumps to CPU 1 and there is no difference. They both keep running with full priority on their CPU and so my program slows down.

You could try to get better results by reducing Prime95's process priority (in the Options menu - unlock with password '9876' and change the priority) and/or use the task manager and increase the priority of the other task's process (right click on the process and change priority).

[akruppa]

I presume Prime95 is already running at idle priority, unless mimic changed the default setting (and then he'd obviously already know about the priority option). If the OS sees an idle cpu, it'll run Prime95 on it, no matter what its priority is. The problem is that the OS does not know that processes on both virtual cpus compete for execution units in the same core.

Alex

[Dresdenboy]

Originally Posted by akruppa

If the OS sees an idle cpu, it'll run Prime95 on it, no matter what its priority is. The problem is that the OS does not know that processes on both virtual cpus compete for execution units in the same core.

I wrote the same ~8 postings above

But you are right about the possibly unchanged priority setting.

If it is a certain application, which is disturbed that much by Prime95, then the user could also stop it quickly in the system tray.

[Jeff Gilchrist]

Based on a lot of recent testing I have found that Windows XP and 2000 are very brain dead when it comes to Hyperthreading (as you have found out).

Linux 2.4 is the same way, but the Linux 2.6 kernel knows about HT and schedules processes based on the fact that the second "processor" is just a virtual one. Much better performance seen with 2.6.

[PhilF]

What flavor of 2.6 are you running?

[dsouza123]

Another option to reduce the CPU time used by Prime95

In prime.ini put the following line
Throttle=n
where n = milliseconds to sleep after each iteration. Try =1000

Unfortunately this will hobble Prime95 all the time,
because it isn't connected to the PauseWhileRunning.


Maybe a ThrottleWhileRunning would be appropriate.


Was the PauseWhileRunning=program1,program2 tried ?
It will effectively keep Prime95 from taking CPU time/FP resources
from the other program.
What about with a small number (for more frequent checking) of the associated line ?
PauseCheckInterval=4

Does Affinity 1 for Prime95 make any difference ?
Are both virtual CPUs treated identically or
is one just given time if the primary is waiting/is stalled ?

[Dresdenboy]

Originally Posted by dsouza123

Does Affinity 1 for Prime95 make any difference ?
Are both virtual CPUs treated identically or
is one just given time if the primary is waiting/is stalled ?

The virtual CPUs are treated identically by the Windows scheduler and AFAIK the virtual CPUs themselves have equal priority.

I agree with you about using the throttle parameter. This should at least improve the situation.

[Jeff Gilchrist]

Originally Posted by PhilF

What flavor of 2.6 are you running?

What do you mean by flavour? I am using the generic kernel from kernel.org (not any patch set version). The version I tested was 2.6.10 or possibly the latest 2.6.11.

[mimic]

Originally Posted by Dresdenboy

I agree with you about using the throttle parameter. This should at least improve the situation.

This sadly does not work for me. The problem is in overall speed for programs I use everyday. So then Prime95 would not get any CPU time as I am running the programs almost always. But even if they run they do not consume CPU all the time (in fact they consume the CPU only in fraction of their runtime - but I would like that in this fraction they work fast).

Of course I can pause the Prime95 every time ... but ... :-)

[RickC]

Interesting. I wonder why setting the Prime95 affinity to 0 fixed my Media Player issue. I double checked the results before I posted them. It really did work and I made sure there were no other variables in the testing.

I didn't test any other programs because I don't have a problem with any others. My computer is very fast whether I have 1 program or 10 open.

I am using Win XP Pro SP2 and my P4 is a 530. According to CPU-Z it is Family F, Ext. Family 0, Model 3, Ext. Model 0, Stepping 4, Revision D0.

I thought of another possibility if you are having problems with a specific program. You could try setting Prime95 affinity to 0 from within Prime95 like I did. Then from the Processes tab of the Windows Task Manager you can set the affinity of the program you are having trouble with to only use CPU 0. Then there is no way it can jump to CPU 1. This is just a thought. I have never tried this because just setting the Prime95 affinity worked for me.

[moo]

why dont you disable HT and try from there it will be a option in ur bios...