Just in Case : Quad core vs Dual core , cores vs base clock

[whitedragon101]

Just in case Apple surprise us with a Sandybridge Quad core, and even if they don't I was wondering the following.

1 ) During sustained use in 3D gaming does a Quadcore with lower clock speeds beat a dual core with higher clock speeds.

2) Can the quoted turbo speeds be achieved in sustained use (ie 3D gaming where maximal load can be applied for a couple of hours).

http://www.anandtech.com/show/4084/intels-sandy-bridge-upheaval-in-the-mobile-landscape

i7-2630QM
Base Frequency 2.0GHz
Max SC Turbo 2.9GHz
Max DC Turbo 2.8GHz
Max QC Turbo 2.6GHz

i7-2620M
Base Frequency 2.7GHz
Max SC Turbo 3.4GHz
Max DC Turbo 3.2GHz
Max QC Turbo N/A

 

[felch]

Its going to depend on how the application is coded. If an application is coded to utilize 1 core then its not going to matter if you have 2 or 400. Newer advances in chip architecture also accounts for why a 2ghz dualcore today is much faster than the offerings 4 years ago.



Processor speed is just as meaningless as the amount of cores you have for 3D gaming. Your video card is the single largest determining factor for the performance of the game.



Try something like a 300+ layer photoshop image or batch processing 50+ 16 megapixel RAW files if you want to see a better comparison IMO.

 

[goMac]

Just in case Apple surprise us with a Sandybridge Quad core, and even if they don't I was wondering the following.

1 ) During sustained use in 3D gaming does a Quadcore with lower clock speeds beat a dual core with higher clock speeds.

Depends entirely on the game. In general, no.

2) Can the quoted turbo speeds be achieved in sustained use (ie 3D gaming where maximal load can be applied for a couple of hours).

Turbo turns off all cores but one to do it's magic, so yes, turbo can be run indefinitely.

Felch is right on the video card. That will be the biggest issue for games, not the processor.

 

[Erasmus]

I believe there is two forms of "turbo" in the new SB CPUs. The first allows one or all of the cores to be overclocked for short periods of time when the CPU is cold, and then throttles back to normal when it starts getting too hot. The second disables or slows some of the cores to allow power to be redirected to those remaining active.

I expect that SB can take advantage of both of these at once, so if you're running a hungry single thread app, it might turbo up 50% for a few minutes, and then drop back to 40% and hold. Clearly the period of time spent in the top performance would depend on the effectiveness of the cooling system.

One thing to consider is that the quad core CPUs should have better cooling systems, both as they have a higher TDP to meet, and the silicon is physically bigger (inside the package) than the duals. Therefore one should expect the quads to hit the max turbo faster and longer than the duals. I would further expect that the CPU would rapidly change the active core to prevent one from wearing out before the rest, which would also help dissipate heat.

 

[whitedragon101]

Turbo turns off all cores but one to do it's magic, so yes, turbo can be run indefinitely.

That is not the case anymore as you can see from my first post (see below). There are 4 figures listed : base frequency then Single Core Turbo, Dual Core Turbo (run 2 cores simultaneously) and Quad Core Turbo (run 4 cores simultaneously).

i7-2630QM
Base Frequency 2.0GHz
Max SC Turbo 2.9GHz
Max DC Turbo 2.8GHz
Max QC Turbo 2.6GHz

Processor speed is just as meaningless as the amount of cores you have for 3D gaming.

This used to be the case but not anymore. As you can see here:
http://www.overclock.net/pc-games/659536-contagion-review-dual-core-vs-quad.html
Battlefield Bad Company 2 runs twice as fast on a quad core. Also apparently GTA IV can split the main processing across 2 cores and run the physics thread on a 3rd increasing performance by 25%. Games are starting to be written to take advantage of Quad core processors but it is unclear to me how widespread this is.

 

[whitedragon101]

I believe there is two forms of "turbo" in the new SB CPUs. The first allows one or all of the cores to be overclocked for short periods of time when the CPU is cold, and then throttles back to normal when it starts getting too hot. The second disables or slows some of the cores to allow power to be redirected to those remaining active.

Thanks Erasmus. I don't suppose you have a link to that info. I have been watching Anandtech like an hawk and they show the 3 turbo speeds I posted above but not how the turbo's behave.

 

[Erasmus]

Thanks Erasmus. I don't suppose you have a link to that info. I have been watching Anandtech like an hawk and they show the 3 turbo speeds I posted above but not how the turbo's behave.

I'm afraid I can't remember where I saw it (or even if I imagined it), but really, it's the only way to explain the four clock speeds you listed.

I'd like to add that quad cores have existed for a while, but they have been for the "enthusiast" market (ie. spec whores). Sandy Bridge makes quad cores somewhere between mainstream and performance level, which is why I think there is an excellent chance of at least some (if not a lot) of quad MBPs soon. Ivy Bridge will apparently make quads the entry level, so next year we'll have quad MacBooks and MBA's.

 

[goMac]

Battlefield Bad Company 2 runs twice as fast on a quad core. Also apparently GTA IV can split the main processing across 2 cores and run the physics thread on a 3rd increasing performance by 25%. Games are starting to be written to take advantage of Quad core processors but it is unclear to me how widespread this is.

Some games might be able to use Quad Core, but on a laptop you're going to hit the GPU as a bottleneck first...