50% cpu workload max????

i just got a used ic7 and 2.4c i have the thremal throttling turned off but when i run prime95 or any other program like that i only get 50% load on my cpu and the system idel process takes the rest.

why is this?

thats because you have a HyperThreading CPU....it makes windows believe you have Dual CPU's which increases performance...

if you were to open a 2nd instance of Prime the you would get 100% max load virtually...

Gods_oMekone said:

i just got a used ic7 and 2.4c i have the thremal throttling turned off but when i run prime95 or any other program like that i only get 50% load on my cpu and the system idel process takes the rest.

why is this?

Click to expand...

Hyperthreading is a technology Intel uses to utilise spare registers and thus appear to have two logical CPUs, each capable of processing a task each at the same time.

As most processes can only use one CPU at a time, the Operating System thinks that you have two CPUs, one is being used fully by a task and so only 50% of the CPU power is being used.

Short answer: Dont worry, its normal

Is it really true, however, that only 50% of the available CPU computational power is being used in such cases? I didn't believe that this was the case. Hmm, I'll have to do a little experiment at home tonight ... -- Paul

let me know what you find out, i really feel like im not stressing my cpu enough @ only 50%

Preliminary testing results:

Test:
Software: I ran some of my tumor growth simulation research. This is a very CPU-intensive, single-threaded app. I ran it at a high spatial resolution, which means that a single complete time step takes on the order of 10-20 minutes at this resolution. Code is C++ compiled with a host of optimizations with GCC.

Running on WinXP SP1a.

I'm going to call 1 unit of work (w) a single time step of the program.

Test 1: Two simultaneous threads, each with (virtual) CPU affinity set to CPU0 and CPU1, respectively for the two threads.

thread1 affinity CPU0
5:53:05 to 6:06:40 = 13 minutes, 35 seconds = 815 seconds
thread2 affinity CPU1
5:53:05 to 6:06:40 = 13 minutes, 35 seconds = 815 seconds

time / work = 815s / 2w = 407.5 s/w

Test 2: One thread with (virtual) CPU affinity set to CPU0.
thread1 affinity CPU0
6:08:00 to 6:18:30 = 10 minutes, 30 seconds = 630 seconds

time / work = 630 s/w

relative difference: (407.5-630)/630 = .35

Preliminary conclusion: I got 35% more computational work done by running two instances in 2 threads than just one thread. Interestingly, on the hyperthreading with each thread given a virtual CPU affinity (so they wouldn't hop from CPU to CPU), each thread completed the unit of work in equal time. That means that each thread gets equal CPU resources internally in the hardware.

I'll recompute these results without the CPU affinity to see if that makes any difference.

I wish I had a non-HT winXP installation to compare with.

This should have interesting consequences for the folding team.

-- Paul

Its not really 50%, its 100% of 1 (virtual) CPU, or 1 thread.

Indeed, that is the case. And it's likely close to 100% of the performance you'd see with hyperthreading disabled. If my testing is any indication, stressing out the single virtual CPU is somewhere in the ballpark of 75% of the total CPU load possible in a HT situation. -- Paul


-- Paul

Is that why I can run folding and games at the same time with little performance differance???

I believe so, in part. Although the lower priority on the folding task certainly has a lot to do with that, too. On the other hand, the folding task will likely compete with all the background processes (and win over them) for one virtual CPU, while the game will take 100% of the other virtual CPU. But the differing priorities between the folding process and the game process will complicate things quite a bit. -- Paul

Why not disable HT in the BIOS and try the test again?

JOn....

Ah, I would, but since the OS has the multiprocessor-based kernel installed, so I don't think the test would be valid. I'm not even sure if the OS would function properly with HT disabled in BIOS but with the multiprocessor-based kernel. -- Paul

It works fine for me. I can enable it and windows will detect both of the "CPUs"

I get better FPS in games and benchmarks with HT disabled.


With 2K it goes crazy though, it will crash sometimes, and not detect the "CPUs" properly other times.