Using Dual Processors in FS-X

[rumpel]

This may have already been discussed, I have not been monitoring the Forum for a couple of weeks. If so pardon the post.

This applies to dual processor systems only. Mine consists of Windows Media edition running two Intel 2.8's. However, I would expect the results to be the same with XP pro.

If I bring FS-X on in the usual way, and use Task Manager to look at the processor performance I see essentially all the load on one chip. The other is fiddling around at a low level with what I assume are the necessary housekeeping tasks not related to FS-X.

I then tried the following-(with FS-X running, but not in full screen)

On Task manager, go to Processes and right click on FS-X. Then select Affinity. Both processors are checked as in use. Uncheck both processors, then reselect (check mark) BOTH of them in sequence. The screen looks just like it did previously, But:--Return Task manager to Performance and minimize it. (Remember this is all with FS-X loaded.)

Now run FS-X Full Screen for a few minutes, and hit Alt-Enter to return to the non-full-screen view. Click on the minimized Task Manager to bring it up, and FS-X will automatically go into Pause mode. Now look at the performance indicators.

At least on my set-up, I see an indication that both processors are now sharing the FS-X load, in fact almost equally, and up to 70% of the full capability of the processors has been utilized. The maximum before was about 53%.

I do not believe this gives me any improvement in FPS, but the Sim seems to run more smoothly in ground movement at high traffic airports, and I have been able to increase aircraft traffic to some extent.

I also believe that that a side effect will be to lessen the mechanical stress on the CPU of one processor heating up under full load while the other loafs, as it was doing previously.

Since I don't really understand what is happening here, if you want to try this, do it at your own risk. I have been running FS-X with both processors active, or at least an indication that they are, for a couple of days now with nothing bad or unusual happening.

If someone understands what this all means, please explain it to me. It was my understanding that you could not use both chips in FS-X. Am I getting a false indication from Task manager, and if so why?

One caveat--I have not yet rechecked the processor temp indicator to see if they are running hotter. That is next on my list.

John

[lalex]

Don't waste any of your time trying to "tweak" the dual core utilization. FSX makes a very specific (and for now, limited) use of the second core and any change that you make - affinity, priority, etc. might potentially only degrade performance.

[loki]

If anything the extra processor usage is because you just minimized FSX and the system is loading up the desktop and other tasks to draw to the screen again. You may also be causing the system to transfer the FSX thread from one processor to the other and adding some additional load because of this. Try going to the Processes tab in the Task Manager to see exactly what FSX is doing and what other processes are running.

The developers have very clearly stated that FSX is largely single threaded, with the exception of a few ares such as loading scenery files. As a single thread cannot be split and processed on two or more cores, only one core will be working on it at any given time. Nothing you do in the Task Manager can change this.

loki

[rumpel]

O.K.-Thanks, and all accepted-but does anyone understand why unchecking and rechecking the two core boxes in Task Manager changes the indication on the performance displays?

John

[loki]

It's likely that it was the act of minimizing FSX that changed the CPU load, not playing with the processor affinity settings.

loki

[rumpel]

Loki;

The only problem with that is that the indicated CPU load change does not occurr unless I go through the process I described of unchecking then rechecking the affinity settings for core 0 and core 1. Also, I am not minimizing FS-X, I am just taking it out of full-screen mode.

Both of you guys obviously understand the workings of FS-X and dual cores better than I do, and I assume both of you have dual core machines. Would either or both of you try the process I described and see if you can determine what is happening?

You have convinced me that it is not improving performance, I just want to understand what it is doing.

John

[remilton]

I heard this described on another forum as a known bug in how Task Manager reports dual core usage.

After playing around with affinities as you have, the OP in that thread posted a snapshot of the Task Manager dual CPU utilization graph.

It looked kind a odd to me and after studying it for a while, it appeared to me that chart trace on the second core was an inverse snapshot of the first core. I imported the image into Photo Shop and inverted the trace of the second core and although there was a small amplitude difference, the two traces were almost identical when laid on top of each other.

I am pretty certain that if you were really seeing improved usage of that second core, you would have to be experiencing better FPS.

Ron

[rumpel]

Ron,

Many thanks. I appreciated the other replies and they were educational to me, but you are the first to answer the specific questions in my post.

I first thought I had stumbled on some sort of real improvement, but that now seems pretty much proven false. I did not see any indisputable quantitative evidence of improvement in FPS, and the smoothing thing was judgemental on my part.

After realizing this, I bacame interested in the peculiarity solely from the standpoint of what was causing it. I believe you have answered that and consider the matter closed.

Regards, Thanks again for sharing your information and test results.

John

[remilton]

You are welcome.:D