Why the reviews test CPUs at different clock speeds against one anothe

[3DCGdesign]

Does anyone know why they test CPUs at different clock speeds against one another? I see it in almost all reviews I read.

Isn't it a bit like testing a horse's speed against a camel? :roll:

 

It seems to me if all CPUs were at the same clock speed, then you could actually see which performs better... I mean of course a 3.2Ghz is faster than a 2.66, duh!?

http://www.anandtech.com/show/2839/5

[Waco]

Clock-for-clock performance is fine if the CPUs are actually sold at the same frequency and price points...but they are not. In the end actual performance is all that matters - the absolute clock speed matters not.

[sdy284]

Clock-for-clock performance is fine if the CPUs are actually sold at the same frequency and price points...but they are not. In the end actual performance is all that matters - the absolute clock speed matters not.

+1

 

that would be like when car magazines test a mustang & camaro, then they tune the engines so that they have exactly the same horsepower. Whats the point in that? People want to know what kind of performance they get then they take out the CPU and plug it in. period.

[ccokeman]

Its just like testing cooler for the CPU. They are different, that is the idea but I can see the thought process behind the question and it is an intriguing thought.

[The Smith]

that would be like when car magazines test a mustang & camaro, then they tune the engines so that they have exactly the same horsepower. Whats the point in that? People want to know what kind of performance they get then they take out the CPU and plug it in. period.

Well said. Car analogies always work well in the CPU world.

[hardnrg]

I mean of course a 3.2Ghz is faster than a 2.66, duh!?

http://www.anandtech.com/show/2839/5

Actually, you've just provided a perfect example of what you have failed to understand.

 

E.g.

 

The i5 750 @ 2.66GHz is better than:

 

Q9650 @ 3GHz

Phenom II X4 @ 3.4GHz

Q8400 @ 2.66GHz

 

Generally, newer and more expensive CPU technology does more work per clock than older/cheaper tech.

[KK_]

the i5 750 (stock 2.66) beats the Q8400 (overclocked 3.2) by about 20Gflops

[ccokeman]

Also you have to look at the underlying architecture to see the L1/L2/L3 cache

[3DCGdesign]

Thanks for the help, foks, that makes sense, I guess.

 

Except that, for me, it's difficult to actually read these reviews keeping in mind that my i7920 is currently running at 3.62 instead of stock 2.66... so when I see the i7 just barely loosing to another cpu like the i7 860, which is running at 2.8, makes me wonder if I can read reviews at all anymore... or maybe I need a tutorial on how to read reviews. (I understand very little about L1,L2,L3 cache for instance)

 

I read this benchmarkreview, and found it most helpful with a somewhat unique? cost/value comparison:

 

After running a benchmark, he then makes a ratio of the cost per score like this...

Looking at performance from a cost-value standpoint, there's a lot more to be learned. Presuming a $300 MSRP, the AMD Phenom-II X6-1090T costs $63.97 per point or multi-core performance and $5.06 per frame of OpenGL performance. Compare this to the $72.35 per point and $4.97 per OpenGL frame for the Intel Core i7-920. The AMD X4-965 costs $61.39 per point, and $3.16 per OpenGL frame. Finally, the Intel Core i7-980X costs $138.89 per multi-core point and $17.14 per OpenGL frame. By this measure, the AMD Phenom-II X6-1090T and X4-965 both offer better 'bang for the buck'.

Maybe if it were in a easy-to-compare chart it would be much handier in a review like this to find the best value:

 

CPU | Price per multi-core score point | Price per frame of OpenGL Performance (Presuming a $300 MSRP)

AMD Phenom-II X6-1090T..$63.97|$5.06

Intel Core i7-920.............. $72.35|$4.97

AMD X4-965 ....................$61.39|$3.16

Intel Core i7-980X ..........$138.89|$17.14

 

I also liked this comparison chart which combines power, speed, # of threads!!!, and cost:

 

Processor Clock Speed Cores / Threads Maximum Single Core Turbo Frequency TDP Price

 

Intel Core i7-975 Extreme 3.33GHz 4 / 8 3.60GHz 130W $999

Intel Core i7 965 Extreme 3.20GHz 4 / 8 3.46GHz 130W $999

Intel Core i7 940 2.93GHz 4 / 8 3.20GHz 130W $562

Intel Core i7 920 2.66GHz 4 / 8 2.93GHz 130W $284

Intel Core i7 870 2.93GHz 4 / 8 3.60GHz 95W $562

Intel Core i7 860 2.80GHz 4 / 8 3.46GHz 95W $284

Intel Core i5 750 2.66GHz 4 / 4 3.20GHz 95W $196