CPU core affinity

Just in case some of you use triple/quad core processors and don't use a software app that automagically distributes WoW's CPU affinity across your cores, here's a bit of into on setting up wow to do this for you.

http://forums.worldofwarcraft.com/th...fHk&rhtml=true

The TL;DR version:

1. Open C:\games\wow\WTF\Config.wtf file.
2. find "processAffinityMask"
3. Default is set to "3" which uses CPU cores 1 and 2
4. To change it to use cores 3 and 4, change value to "12"
5. To change it to use cores 2 and 3, change value to "6"
6. To change it to use cores 1 and 3, change value to "5"

See thread for other combinations and caveats.

TL;DR Part Dos, aka "No, I'm not wrong. And yes, you might think you're doing it right, but you're really Doing It Wrong(tm)."

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You can use this to let WoW run on a specific core(s) but it only works up to two cores. If you set it on 15, you just let the game use 2 out of your 4 processors but you didn't tell it which ones.

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Q u o t e:


So if I am understanding correctly, WoW still only uses two cores, while Windows will, instead of using the same two 'default' cores, be split into other, unused, cores?

Core 1-----Core 2------Core 3------Core 4
WoW--------WoW---------Windows etc.

I dont know much about this whole thing but bottom line, when will WoW itself use four-cores?

World of Warcraft is capped to two cores because we set the default processaffinitymask to 2. There's actually quite a few threads that the game runs but mainly 2 or 3 decent-sized ones and a dozen little ones. Windows can distribute all of these among other cores if you tell it to but you can't specifically tell what thread will go where.

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Note the part in bold/underline in that last sentence. It is a critical point. ;) I leave the why as an exercise to the reader.

whoops... wish I could delete my posts.. asked a question before I read the link

disregard

basically use 255 and you're done for up to 8 cores (i7)

is it possible to make it use more then 2 at a time?

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Originally Posted by Moorea

basically use 255 and you're done for up to 8 cores (i7)

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No. Unless something has changed that I haven't seen a blue post on, WoW will only use the first two cores that it is assigned affinity to. If you want it to use cores 3 and 4, you MUST assign affinity to cores 3 and 4 ONLY.

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Originally Posted by Moorea

basically use 255 and you're done for up to 8 cores (i7)

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Is that what they use? God, I remember using 8-bit notation to design fonts for the Commodore 64. :o

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Originally Posted by Ughmahedhurtz

No. Unless something has changed that I haven't seen a blue post on, WoW will only use the first two cores that it is assigned affinity to. If you want it to use cores 3 and 4, you MUST assign affinity to cores 3 and 4 ONLY.

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I use 255 and it works fine - if you don't set anything it will be the first 2 cores (because the value in the config.wtf is 3) which is maybe what you remember

setting 255 assigns affinity to all 8 cores

You can also open up TaskMan win Vista and Windows 7 can re assign affinity on the fly

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Originally Posted by Moorea

I use 255 and it works fine - if you don't set anything it will be the first 2 cores (because the value in the config.wtf is 3) which is maybe what you remember

setting 255 assigns affinity to all 8 cores

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If you're saying it's OK because you look in task manager and see a checkbox next to all 4 cores and thinking that means it's actually using all 4 cores, I suspect you'd be mistaken. ;)

Well slap my ass and call me sally...I was wrong. Looks like they finally fixed it. 255 or 15 both seem to utilize 4 cores (albeit cores 1, 2 and 4 seem to be used and not much of 3 for some reason), though setting it to 255 causes wow to reset it to 0 when you exit the game the next run. Strange. Either way, this is good!

[edit] For normal Core2Quad Q-series CPUs and AMDs, any setting should work. For i7/nehalem CPUs, 255 affinityMask is bad. You do NOT want WoW using your HT cores--only your physical cores. See this thread for further info on how to set that. See original thread for Blue confirmation that using HT cores = bad.

Here's a blue post stating that WoW really doesn't do much with more than 2 cores, which I think I misunderstood to say that it was related to affinity. :P My bad! /drunk

[edit] Nope, not THAT /drunk. Original blue that prompted this post (also linked in the OP):

http://forums.worldofwarcraft.com/th...geNo=1&sid=1#4

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You can use this to let WoW run on a specific core(s) but it only works up to two cores. If you set it on 15, you just let the game use 2 out of your 4 processors but you didn't tell it which ones.

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Quote:

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Q u o t e:


So if I am understanding correctly, WoW still only uses two cores, while Windows will, instead of using the same two 'default' cores, be split into other, unused, cores?

Core 1-----Core 2------Core 3------Core 4
WoW--------WoW---------Windows etc.

I dont know much about this whole thing but bottom line, when will WoW itself use four-cores?

World of Warcraft is capped to two cores because we set the default processaffinitymask to 2. There's actually quite a few threads that the game runs but mainly 2 or 3 decent-sized ones and a dozen little ones. Windows can distribute all of these among other cores if you tell it to but you can't specifically tell what thread will go where.

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Note the part in bold/underline in that last sentence. It is a critical point. ;) I leave the why as an exercise to the reader.