How to determine which CPU is faster by just looking at specs?

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MoreDents

Limp Gawd
Joined
Mar 9, 2008
Messages
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Ok, I have the latest 24" iMac 3.06 GHz Intel Core 2 Duo and I want to know if its CPU processing speed is faster than my Q6600 2.40 GHz Quad Core
(let's just say all the other specs are the same)

What's the formula for figuring this out? Teach me to fish and not hand me a fish! :D
 
Well, with Core 2 CPUs, there are a few criteria. First of all, there's the CPU speed obviously. Your iMac has a faster speed than the Q6600, so in that respect it is better. However, the Q6600 also has more cores. The additional cores will benefit it only in properly multi-threaded applications; in those applications, the Q6600 will be much faster, but in single-threaded applications, the iMac's CPU will be better.

There is also the amount of cache the CPU has; in general, the more cache, the better the CPU will perform, although the benefit depends on the application, and also, cache differences don't make as much of a difference when you're already starting from a fairly large amount of cache (for example, a CPU with 6MB of cache won't be that much faster than one with 4MB of cache, but a chip with 2MB of cache can be much faster than one with 1MB of cache in certain applications).

Another factor is the FSB speed, although in practice it doesn't make a huge difference. The higher the FSB speed, the better. And the last major thing is the version of the CPU. There are two main versions of Core 2 CPUs, the older one being made on a 65nm manufacturing process and the newer one on a 45nm process. The 45nm chips have several design improvements compared to the older 65nm chips, so depending on the situation, they can be up to 10% or 15% faster, although in most cases the difference is not that significant. Your iMac probably uses one of the newer 45nm CPUs, whereas the Q6600 is an older 65nm chip.
 
It depends a lot on the types of applications used. Right now your dual core would be better due to its higher clock speed over the quad and the scarcity of multi-threaded applications means the focus is more on single core speed. When more applications become multi-threaded, the quad would win simply because it has more cores and would be more efficient in processing.

To put it simply:
Assuming they are essentially the same architecture, in a single threaded app, it would be 3.06GHz vs 2.4GHz; the winner would be the 3.06 due to more processing power. In a multi-threaded app (assuming it is able to use 2 or more cores) it would be (3.06GHz, 3.06GHz) vs (2.4GHz,2.4GHz,2.4GHz,2.4GHz) so the winner would be the quad because it is more efficient by being able to offload additional work to the other two cores.

Generally a processor's speed is determined by:
IPC of the processor
Core clock speed
FSB speed
Cache size (if you do a lot of fetching)

for multi-threaded (if a app takes advantage of two cores or more than two cores):
number of cores

for single-threaded:
Core clock speed
 
Thank you both Zero82z and lostnkonfused for the great thorough replies!!! You've taught me how to fish for sure! :p

I'm mainly using it for Photoshop, which I believe for the most part to be single threaded

So a cheap 3.16Ghz Dual Core would be better for Photoshop than an expensive Core i7 2.66GHz?
 
MoreDents said:
So a cheap 3.16Ghz Dual Core would be better for Photoshop than an expensive Core i7 2.66GHz?
Click to expand...
No. The Core i7 uses a different architecture which is faster than older Core 2 CPUs. Most of the information above doesn't apply to Core i7 CPUs, only to Core 2 chips.
 
Core i7 has better IPC so it can get more work done per clock cycle. Also since the i7 does not rely on the motherboard's northbridge to communicate to RAM, it has lower latency and greater memory bandwidth compared to Core 2 series; this is good for photoshop rendering and such where large amounts of RAM may be needed.
 
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