Dual Processor PowerMacs slow Doom III.

Little Endian

macrumors 6502a
Original poster
Apr 9, 2003
677
31
Honolulu
While I was experimenting with Doom III settings and benchmarking with the timedemo I realized that if I disabled my second CPU on my Dual 2.5Ghz G5 I could get a 33% performance bump. I used the CHUD tools to disable the second processor.

With two 2.5Ghz Chips running with my Geforce 6800GT I was able to get 32.7 FPS at 1680x1050 resoultion High settings with all Advanced options on except for Vsync and FSAA. Aniso was set to the standard 8x. However upon disabling the second processor I get 43.2 FPS at the exact same settings and resolution. I can even bump up to Ultra Quality settings and still get 42 FPS in the timedemo!

I know it sounds weird and it is weird because I only get this bump from disabling the the second CPU at a resolution of 1680x1050 and with FSAA off. Having one or two proccessors on made no difference if I had FSAA running at any resolution or setting. Perhaps folks with a Dual CPU configuration machine can check for me as well. I am interested if others see this at resolutions higher than 1680x1050 like the standard 1600x1200 or at 1920x1200. I got no speed improvement from disabling the processor at lower resolutions and FSAA still kills performance but something is deffininitely not right.
 

JeDiBoYTJ

macrumors 6502a
Jun 22, 2004
859
0
Ft. Lauderdale, FL
interesting observation...

my only guess, is that the game is *trying* to take advantage of the 2 CPUs in the game when its at higher resolutions, while *trying* to balance the load onto both CPUs... but since the game doesnt support it, the CPU cycles are lost.

just a quick guess, lol... but interesting observation none the less
 

grabberslasher

macrumors 6502
Aug 2, 2002
409
1
Éire
Little Endian said:
While I was experimenting with Doom III settings and benchmarking with the timedemo I realized that if I disabled my second CPU on my Dual 2.5Ghz G5 I could get a 33% performance bump. I used the CHUD tools to disable the second processor.

With two 2.5Ghz Chips running with my Geforce 6800GT I was able to get 32.7 FPS at 1680x1050 resoultion High settings with all Advanced options on except for Vsync and FSAA. Aniso was set to the standard 8x. However upon disabling the second processor I get 43.2 FPS at the exact same settings and resolution. I can even bump up to Ultra Quality settings and still get 42 FPS in the timedemo!

I know it sounds weird and it is weird because I only get this bump from disabling the the second CPU at a resolution of 1680x1050 and with FSAA off. Having one or two proccessors on made no difference if I had FSAA running at any resolution or setting. Perhaps folks with a Dual CPU configuration machine can check for me as well. I am interested if others see this at resolutions higher than 1680x1050 like the standard 1600x1200 or at 1920x1200. I got no speed improvement from disabling the processor at lower resolutions and FSAA still kills performance but something is deffininitely not right.
I bet it's because OS X by default is trying to split the load between the 2 processors, which the game probably doesn't like.

This way, you're getting 100% of one processor.

The deal with fps is that there's a slowdown in Apple's OpenGL so you're probably not going to get faster fps until OpenGL is changed.
 

psycho bob

macrumors 6502a
Oct 25, 2003
638
6
Leeds, England
This wouldn't be that suprising actually. It was discussed on another thread how poorly OS X actually handles the two CPU's and how tasks jump between them when it isn't necessary. That is why I'm so suprised people are jumping up and down at the thought of having 4 3GHz cores in their machines. Unless Tiger drastically improves the scheduler and some of the more basic functions of the OS then all that CPU power will just be wasted. Two G5's could perform so much better if apple put the time in to getting the code right.
Another question is who will actually write programs to take advantage of 4 cores, games developers can't be bothered to even enable SMP support for 2 CPU's so they won't and I can't see adobe doing it either at least not yet.
The main thing though about using both CPU's in a G5 is while playing Doom 3 you could also be working in Photoshop, perhaps on iChat maybe even listening to iTunes if you didn't want the full scary sinister dark gameplay factor. Dual machines rock but they could be so much better, for me a quad core machine would only provide bragging rights at this stage which is sad really :(
 

psycho bob

macrumors 6502a
Oct 25, 2003
638
6
Leeds, England
ChrisFromCanada said:
I would be happy to try that for you but I am not sure where the CHUD tools are and how to use them. Maybe you could write a small guide for those who are interested.
First you need to have the developer tools installed on your machine.
You can download the latest CHUD tools from here http://developer.apple.com/tools/performance/
The link on the page is for an FTP connection it might say it cannot connect but then just appears anyway. The latest version is 4.1.1.
You must install the developer tools first though or it errors!! Once you've installed the CHUD tools (if you install from the developer CD that came with the OS have a hunt through the developer folder until you find CHUD then you should be able to install from there) there should be a hardware icon added to system preferences. From there you can disable the CPU's and play around. Remember these are developer tools though so read up first on what they can do and if your unsure don't click on anything.
 

Dont Hurt Me

macrumors 603
Dec 21, 2002
6,056
6
Yahooville S.C.
Now wouldnt you have thought Aspyr,Apple,id would have discovered this? amazing! turn off 1 cpu and presto! All 3 of those guys have work to do that is clear. this flabergasts me. Good discovery by Little Endian.
 

Soulstorm

macrumors 68000
Feb 1, 2005
1,887
1
Yeap, it works!!

I haven't run any benchmarks... but I have noticed an approximately 30% increase in performance.

This is remarkably...inexplicable! I think all benchmarks should be run with one processor on, and not two!
 

Little Endian

macrumors 6502a
Original poster
Apr 9, 2003
677
31
Honolulu
grabberslasher said:
I bet it's because OS X by default is trying to split the load between the 2 processors, which the game probably doesn't like.

This way, you're getting 100% of one processor.

The deal with fps is that there's a slowdown in Apple's OpenGL so you're probably not going to get faster fps until OpenGL is changed.
Yes that is exactly my conclusion as well. I am no professional when it comes to programming but something is surely wrong with how Doom III is being handled on Dual CPU machines. I decided to run Doom III in windowed mode with both activity monitor and terminal running. When both processors are running I noticed that Doom III sets my CPU monitor usage back and forth rapidly and that threads from Doom III are being bounced back and forth from CPU to CPU.

Mac OSX is not perfect in multi-tasking and scheduling of CPU usage but it's not supposed to be this bad either. Usually there is only a small 5%-10% speed penalty if any caused from overhead when running an App or Game that is not SMP aware on an MP system. In many other cases there is no overhead at all. In fact with most Games even ones that are not SMP aware they still peform equally or better on MP systems compared to a single CPU setup.
 

patseguin

macrumors 68000
Aug 28, 2003
1,551
446
I was running Doom 3 on my 6800 Ultra and it performed like crap. I took it out and put in my x800 again and it was TONS better. I had the same result with WoW.
 

applekid

macrumors 68020
Jul 3, 2003
2,098
0
Dont Hurt Me said:
Now wouldnt you have thought Aspyr,Apple,id would have discovered this? amazing! turn off 1 cpu and presto! All 3 of those guys have work to do that is clear. this flabergasts me. Good discovery by Little Endian.
My thoughts exactly. This is a surprising find and a good one, too. :cool:

Somebody needs to bring this up to Aspyr and Apple. Also, this is definitely newsworthy and should be reported to some Mac news websites.
 

Lacero

macrumors 604
Jan 20, 2005
6,639
2
I'm going to try and benchmark it on my Dual G5 PM and report the results. I just have to figure out this CHUD thing... :confused:
 

broken_keyboard

macrumors 65816
Apr 19, 2004
1,144
0
Secret Moon base
I think ~loserman~ explained this on another thread. When OS X is swapping between the various programs that are running at any one time, it doesn't necessarily put the prog back on the same CPU it was last running on. So therefore you don't get the same cache benefits.

When you disable one CPU, it always puts it back on the same CPU where there is stuff cached from last time.
 

Dont Hurt Me

macrumors 603
Dec 21, 2002
6,056
6
Yahooville S.C.
Soulstorm said:
I haven't run any benchmarks... but I have noticed an approximately 30% increase in performance.

This is remarkably...inexplicable! I think all benchmarks should be run with one processor on, and not two!
did you run it at 1280 x 1024?
 

JamSoft

macrumors member
Jun 30, 2002
62
0
Rockford, MI
Results

My Computer:
Power Mac G5
Dual 2.5 GHz
Memory: 4 GB

Graphics Card:
GeForce 6800 Ultra
VRAM (Total): 256 MB

Mac OS X:
System Version: Mac OS X 10.3.8 (7U16)

Mac System Settings / Options
Processor Performance: Highest
ALL User programs / apps were quit. Used Activity monitor to verify.

__________ Game Settings __________
• Video Quality: High Quality
• Screen Size: 1280 x 1024
• Fullscreen: Yes
• High Quality Effects: Yes
• Enable Shadows: Yes
• Enable Specular: Yes
• Enable Bump Maps: Yes
• Vertical Sync: No
• Antialiasing: Off

__________ My Custom Tweaks __________
– all .pak files were 'unzipped' / decompressed
image_useCache 1
image_cacheMegs 512
imagecacheMink 3072
____________________

Results:

Both CPU's On:
• First Run: 33.7 FPS
• Second Run: 37.1 FPS

Only 1 CPU On:
• First Run: 41.8 FPS
• Second Run: 46.7 FPS
____________________________________________________________


As you can see, by turning the 2nd CPU off, the results definitely increased. I still can't believe that I only average MAX 46.7 FPS with my computer. Such a shame.

I don't want to sacrifice video quality, so if there are any other tweaks / suggestions for boosting FPS or loading that DO NOT sacrifice quality — let me know. :cool:

Also, if anyone would like me to do any other new/different tests, just ask.

Thanks,
Nate
 

Lacero

macrumors 604
Jan 20, 2005
6,639
2
JamSoft said:
As you can see, by turning the 2nd CPU off, the results definitely increased. I still can't believe that I only average MAX 46.7 FPS with my computer. Such a shame.
No kidding. On such a top of the line PM/Video card, I would expect at least 80 FPS at 1600x1200 and 55 fps with 4xAA.
 

Dont Hurt Me

macrumors 603
Dec 21, 2002
6,056
6
Yahooville S.C.
JamSoft said:
My Computer:
Power Mac G5
Dual 2.5 GHz
Memory: 4 GB

Graphics Card:
GeForce 6800 Ultra
VRAM (Total): 256 MB

Mac OS X:
System Version: Mac OS X 10.3.8 (7U16)

__________ Game Settings __________
• Video Quality: High Quality
• Screen Size: 1280 x 1024
• Fullscreen: Yes
• High Quality Effects: Yes
• Enable Shadows: Yes
• Enable Specular: Yes
• Enable Bump Maps: Yes
• Vertical Sync: No
• Antialiasing: Off

__________ My Custom Tweaks __________
– all .pak files were 'unzipped' / decompressed
image_useCache 1
image_cacheMegs 512
imagecacheMink 3072
____________________

Results:

Both CPU's On:
• First Run: 33.7 FPS
• Second Run: 37.1 FPS

Only 1 CPU On:
• First Run: 41.8 FPS
• Second Run: 46.7 FPS
____________________________________________________________


As you can see, by turning the 2nd CPU off, the results definitely increased. I still can't believe that I only average MAX 46.7 FPS with my computer. Such a shame.

I don't want to sacrifice video quality, so if there are any other tweaks / suggestions for boosting FPS or loading that DO NOT sacrifice quality — let me know. :cool:

Also, if anyone would like me to do any other new/different tests, just ask.

Thanks,
Nate
Thats a very big improvement. You should send this to Aspyr,id,& Apple. Still who would have thought to think different? ;)
 

Little Endian

macrumors 6502a
Original poster
Apr 9, 2003
677
31
Honolulu
I sent a message to Glenda Adams of Aspyr Media regarding this Dual Processor slow down and have yet to wait for a reply. I have also contacted Rob_Art Morgan of Barefeats.com and hopefully he will look into it and post his findings on his Mac benchmarking website.
 

TheGimp

macrumors 6502
Jun 14, 2004
391
0
anywhere, usa
MacsRgr8 said:
Cool :cool:

I'm gonna test my setup too!

Dual 1.8
2 GB
6800 Ultra

Get back tonite (CET that is)

Nice one, Little Endian
Help! Chud won't install on my computer. It reports that it "can't be installed on this computer". How do I get around this?
 

Soulstorm

macrumors 68000
Feb 1, 2005
1,887
1
Dont Hurt Me said:
did you run it at 1280 x 1024?
Yes, I did, and the performance increase is 30%.

EDIT: No, I didn't I run it 1024x768 at Ultra High and all setting enabled except antialiasing and vertical sync.

Someone please, bring this up to Aspyr and Apple!!
Macologist already knows that issue...
 

MacsRgr8

macrumors 604
Sep 8, 2002
7,830
1,120
The Netherlands
It's the same for me!!

Here we go:

PowerMac Dual 1.8 GHz G5
2 GB RAM
nVidia GeForce 6800 Ultra
2 x 160 GB S-ATA HD RAID0

Doom 3 settings:
1600 x 1200
High Quality
Advanced default (= Shadows on, AA off etc)

"Timedemo demo1":

Dual CPU:
1st: 27.7 fps
2nd: 32.7

Single CPU:
1st: 28.3
2nd: 36.1

as these settings are a real burden on the grfx card, I'd say this is a huge increase... :cool:
 

Lacero

macrumors 604
Jan 20, 2005
6,639
2
BUNK. I tried it on my G5 PM and noticed no increase in fps performance. It actually decreased. Sorry, but I think 30% increase is not possible from the results of my test.