How do quad-cores decide which cores to run?

[SweeJ]

hi there,

i have quite an old AMD64 3500+ system which i assembled over 3 years ago, and think it's a good time to jump on the multi-core bandwagon. i'm thinking of the Intel Core2 Quad Q9550. since i tend to only upgrade/change system every 3+ years, i thought perhaps the Q9550 right now would be a good buy till my next purchase.

my usual usage pattern would be: running several web browser windows with many tabs per browser, word processing, outloook, MSN Messenger, anti-virus background, playing music and occasional videos, torrents and gaming. i do all of that at the same time, and yes, i do game and alt-tab out very often. and even when i'm not actively playing, i like to keep the game running in the background as i hate reloading times. also, most of the games i play i've noted are not multi-threaded.

my questions are:

1. since i do game 50% of the time, and based on my usage pattern, will i benefit more from faster clocked dual-core or slower clocked quad-core? whilst i hate slow fps, i still find slow alt-tabbing annoying as well (i notice that is very obvious in Vista vs my XP system).

2. in the quad-core, is each core dedicated to one task? ie. gaming core 1, webbrowsing core 2, playing music core 3, misc core 4? or do all 4 cores just share and divide tasks equally? and how does it work if the game is multi-threaded?

3. how does the CPU decide which core to run on simple tasks? as this PC runs 24/7, there will be many hours it will be rather idle eg, just torrents running. will core number 1 will be the active one? i don't like the idea that particular core just keeps working whilst the other cores are inactive.... will that core increase the chances of it being "burned out"?

4. this is rather cpu-video related if i decide to get the ATI 4870 x2, will it be CPU bound to the Q9550? or will the 4870 1GB suffice? or alternatively, shud i go for a faster CPU?

sorry about all these question and if it seems rather nooby i don't really know how multi-cores work.

thanks for ur replies in advance! ^^

 

[cmdrdredd]

Originally posted by: SweeJ
hi there,

i have quite an old AMD64 3500+ system which i assembled over 3 years ago, and think it's a good time to jump on the multi-core bandwagon. i'm thinking of the Intel Core2 Quad Q9550. since i tend to only upgrade/change system every 3+ years, i thought perhaps the Q9550 right now would be a good buy till my next purchase.

my usual usage pattern would be: running several web browser windows with many tabs per browser, word processing, outloook, MSN Messenger, anti-virus background, playing music and occasional videos, torrents and gaming. i do all of that at the same time, and yes, i do game and alt-tab out very often. and even when i'm not actively playing, i like to keep the game running in the background as i hate reloading times. also, most of the games i play i've noted are not multi-threaded.

my questions are:

1. since i do game 50% of the time, and based on my usage pattern, will i benefit more from faster clocked dual-core or slower clocked quad-core? whilst i hate slow fps, i still find slow alt-tabbing annoying as well (i notice that is very obvious in Vista vs my XP system).

2. in the quad-core, is each core dedicated to one task? ie. gaming core 1, webbrowsing core 2, playing music core 3, misc core 4? or do all 4 cores just share and divide tasks equally? and how does it work if the game is multi-threaded?

3. how does the CPU decide which core to run on simple tasks? as this PC runs 24/7, there will be many hours it will be rather idle eg, just torrents running. will core number 1 will be the active one? i don't like the idea that particular core just keeps working whilst the other cores are inactive.... will that core increase the chances of it being "burned out"?

4. this is rather cpu-video related if i decide to get the ATI 4870 x2, will it be CPU bound to the Q9550? or will the 4870 1GB suffice? or alternatively, shud i go for a faster CPU?

sorry about all these question and if it seems rather nooby i don't really know how multi-cores work.

thanks for ur replies in advance! ^^

1) For gaming a quad is a marginal difference right now. Having said that, it's better for just about everything else that can use more than one core at a time. Windows tries to spread the tasks around between what's available, not always 100% perfect but it seems to try running things evenly.

2) As I said before, it spreads the work around. You can manually set an application to use only a specific core and set another app to a different core. You do this through task manager. It works, but I don't bother because there's no benefit that I can see to doing this. In a game that can use more than one core, it spreads out the work load between the cores. No core is at 100% but you may see one at 60% one at 40% and one at 30% depending on what work it is given. This is up to the individual game and usually doesn't help much over a faster clocked Dual Core.

3) There will be no burn out of one core. Think of each core as an individual CPU that will do what its told. If you're running just one app the work is spread between each core a bit. No core will ever be pegged to 100% unless you tell it to.

4) a videocard will not be limited by your Q9550. You see, at high resolutions with AA and AF the video card has more work to do than the CPU and typically the video card becomes the weak point. A faster dual core (say a E8500/8600 @ ~4Ghz) will always be faster in general gaming tasks than a Q9550 which is clocked lower, but you will not be CPU limited after say 3Ghz. If you tried running 1280x1024 every day then maybe it would make more of a difference because the GPU won't even break a sweat. at 1680x1050 or 1900x1080/1900x1200 the GPU is the main concern. It would depend on what you want out of your games. If you run 1900x1200 and want to turn on 4xAA and 16xAF all the time then a 1GB 4870 may not cut it for everything (obviously crysis will be slower than everything else).

my overall recommendation is to get the Q9550 because in the future more and more things will start using all 4 cores and the performance delta between a dual and a quad will open up significantly. Right now it's not a big deal, but if you don't plan to get a new system next year then I'd go with a quad now. The i7 isn't a huge leap over a current C2Q and the Phenom II seems to be in the range of a C2Q in terms of performance per Mhz, at least by early reports and rumors. I just got my Q9550 and am very pleased. 3.6Ghz is a very easy overclock to achieve and won't push your components too hard. This system I have will last me a long time to come. Simply swap the video card out and I'm good to go.

 

[Flipped Gazelle]

+1 for everything cmdrdredd said.

 

[SweeJ]

cmdrdred, many thanks for ur reply. i think i'll go ahead with my purchase.