WMV HD vs. Prime95

RickC · 2005-02-23, 03:59

I can reproduce over and over that Prime95 makes Media Player 10 choppy when playing 1080p high definition video. A good example is the 1080p download of Striker from:
http://www.microsoft.com/windows/win...tShowcase.aspx

I'm running Windows XP Pro SP2 on a Dell Dimension 8400, 3Ghz Prescott, 800Mhz bus, hyperthreading enabled, 1GB 533Mhz DDR2 RAM, 128MB video card running dual monitors. LL testing a 10,000,000 digit prime with no other applications open. I had plenty of available RAM when I was testing this. My computer passes the Microsoft/Futuremark WMV HD tests with room to spare.

This is just an observation, not a problem for me. I don't actually watch HD stuff. I was just checking out the HD previews.

I was thinking about some possible reasons that I haven't though all the way through (just throwing ideas out):
1. The XP time slicer may not be perfect.
2. The CPU priority may not directly take into account memory bandwidth usage.
3. Processor throttling. I doubt it because it's only 68F in here and both computer fans are working unobstructed. One fan is connected directly to a processor shroud.

Anyone have any other ideas? Has anyone else tried WMV HD?

PhilF · 2005-02-23, 04:40

Try it with Hyper-Threading turned off (usually a setting in the BIOS allows you to turn it off). With it on, Prime95 gets to "steal" some CPU cycles even though it is running at low priority. For the purposes of this test, be sure nothing except Prime95 and Windows Media Player is running.

-Phil

dsouza123 · 2005-02-23, 18:08

Contention for floating point (SSE2).
CPU affinity, which CPU is Prime95 set to.

PhilF · 2005-02-24, 00:36

Also, you can probably fix this problem by adding a line to your prime.ini file. Here is an excerpt from undoc.txt:

In rare cases, users have reported the program can interfere with the
performance of some programs such as disk defragmenters and some games.
You can pause prime95 automatically when these programs are running by
adding this line to prime.ini:
PauseWhileRunning=prog1,prog2,prog3,etc
Note that prime95 will pause if the program name matches any part of the
running program's file name. That is "foobar" will match "c:\foobar.exe",
"C:\FOOBAR\name.exe", and even "C:\myfoobarprog.exe". By default, prime95
will check the list of running programs every 64 iterations, but not more
frequently than every 10 seconds. You can adjust the time period with this
prime.ini setting:
PauseCheckInterval=n
where n is the number of seconds between checking which programs are running.

-Phil

RickC · 2005-02-26, 19:27

I am running Prime95 version 23.8.1. I had hyperthreading enabled in the BIOS and the Prime95 affinitiy set to "Let program run on any CPU". This is the configuration that resulted in the choppy WMV HD.

I disabled hyperthreading in the BIOS and the WMV HD was no longer choppy.

Then I enabled hyperthreading in the BIOS and set the Prime95 affinity to 0. The WMV HD is not choppy in this configuration either.

I looked around the forum and I didn't see any other posts recommending setting the affinity to 0 in a single CPU hyperthreading machine. Setting it this way makes sense to me because Prime95 probably doesn't know the difference between a real second processor and a "logical" second processor. In this configuration I can still have the benefits of hyperthreading without having Prime95 interfere with the hyperthreading.

Rick

2005-02-23, 03:59	#1
RickC Mar 2003 3²×5 Posts	WMV HD vs. Prime95 I can reproduce over and over that Prime95 makes Media Player 10 choppy when playing 1080p high definition video. A good example is the 1080p download of Striker from: http://www.microsoft.com/windows/win...tShowcase.aspx I'm running Windows XP Pro SP2 on a Dell Dimension 8400, 3Ghz Prescott, 800Mhz bus, hyperthreading enabled, 1GB 533Mhz DDR2 RAM, 128MB video card running dual monitors. LL testing a 10,000,000 digit prime with no other applications open. I had plenty of available RAM when I was testing this. My computer passes the Microsoft/Futuremark WMV HD tests with room to spare. This is just an observation, not a problem for me. I don't actually watch HD stuff. I was just checking out the HD previews. I was thinking about some possible reasons that I haven't though all the way through (just throwing ideas out): 1. The XP time slicer may not be perfect. 2. The CPU priority may not directly take into account memory bandwidth usage. 3. Processor throttling. I doubt it because it's only 68F in here and both computer fans are working unobstructed. One fan is connected directly to a processor shroud. Anyone have any other ideas? Has anyone else tried WMV HD?

2005-02-26, 19:27	#5
RickC Mar 2003 2D₁₆ Posts	more info and two solutions I am running Prime95 version 23.8.1. I had hyperthreading enabled in the BIOS and the Prime95 affinitiy set to "Let program run on any CPU". This is the configuration that resulted in the choppy WMV HD. I disabled hyperthreading in the BIOS and the WMV HD was no longer choppy. Then I enabled hyperthreading in the BIOS and set the Prime95 affinity to 0. The WMV HD is not choppy in this configuration either. I looked around the forum and I didn't see any other posts recommending setting the affinity to 0 in a single CPU hyperthreading machine. Setting it this way makes sense to me because Prime95 probably doesn't know the difference between a real second processor and a "logical" second processor. In this configuration I can still have the benefits of hyperthreading without having Prime95 interfere with the hyperthreading. Rick

2005-02-23, 04:40	#2
PhilF Feb 2005 Colorado 1222₈ Posts	Try it with Hyper-Threading turned off (usually a setting in the BIOS allows you to turn it off). With it on, Prime95 gets to "steal" some CPU cycles even though it is running at low priority. For the purposes of this test, be sure nothing except Prime95 and Windows Media Player is running. -Phil

2005-02-23, 18:08	#3
dsouza123 Sep 2002 662₁₀ Posts	Contention for floating point (SSE2). CPU affinity, which CPU is Prime95 set to.

2005-02-24, 00:36	#4
PhilF Feb 2005 Colorado 292₁₆ Posts	Also, you can probably fix this problem by adding a line to your prime.ini file. Here is an excerpt from undoc.txt: In rare cases, users have reported the program can interfere with the performance of some programs such as disk defragmenters and some games. You can pause prime95 automatically when these programs are running by adding this line to prime.ini: PauseWhileRunning=prog1,prog2,prog3,etc Note that prime95 will pause if the program name matches any part of the running program's file name. That is "foobar" will match "c:\foobar.exe", "C:\FOOBAR\name.exe", and even "C:\myfoobarprog.exe". By default, prime95 will check the list of running programs every 64 iterations, but not more frequently than every 10 seconds. You can adjust the time period with this prime.ini setting: PauseCheckInterval=n where n is the number of seconds between checking which programs are running. -Phil