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CPU Speed and No. of Cores

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August 24, 2011 1:57:21 PM

Hello,

I have a server with " 4 cpu's(cores) , each 4.7 GHz"
another server with " 8 cpu's(cores) , each 2.8 GHz"
so will there be a difference in the performance ?

More about : cpu speed cores

a c 159 à CPUs
August 24, 2011 3:28:57 PM

Hi and welcome to Tom's forum.

Sure it is, more cores are always better than core speed. Just to know, how do you get those 4 cores to 4.7GHz?
a c 318 à CPUs
August 24, 2011 4:01:41 PM

chetanshinde said:
Hello,

I have a server with " 4 cpu's(cores) , each 4.7 GHz"
another server with " 8 cpu's(cores) , each 2.8 GHz"
so will there be a difference in the performance ?


It depends.

If your workload can keep 8 cores fully busy, then 8 cores may be better.
If not, then 4 faster cores may be better and response time will be better.

The key is utilization, regardless of 4/8 cores. Once you start to go over say 75% utilization, queue lengths will build and responsiveness will suffer.
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August 24, 2011 4:50:50 PM

geofelt said:
It depends.

If your workload can keep 8 cores fully busy, then 8 cores may be better.
If not, then 4 faster cores may be better and response time will be better.

The key is utilization, regardless of 4/8 cores. Once you start to go over say 75% utilization, queue lengths will build and responsiveness will suffer.


Agreed. More cores doesn't mean faster performance, the question comes into how many threads are being saturated / utilized and the type of data being processed. If your application(s) can utilize more than 4 threads of data, then the 8 core system should perform better.

On the flip side, if your application(s) only use 1-4 threads, then the faster clock speed of the 4 core system will be more beneficial.


a c 201 à CPUs
August 24, 2011 5:05:00 PM

It also depends on what the CPUs are, if the 8 core server is an older dual Core 2 Quad system and the 4 core server is using a Nehalem or Sandy Bridge based chip it would perform better in many cases, especially if it has hyper threading to go with its 4 cores.
a c 318 à CPUs
August 24, 2011 5:05:43 PM

As a simplistic exercise, 4.7 x 4 cores = 18.8
2.8 x 6 = 16.8
2.8 x 7 = 19.6

It will take an average utilization of 7 cores to beat the throughput of the faster 4.7 4 core system.
August 24, 2011 5:09:25 PM

geofelt said:
As a simplistic exercise, 4.7 x 4 cores = 18.8
2.8 x 6 = 16.8
2.8 x 7 = 19.6

It will take an average utilization of 7 cores to beat the throughput of the faster 4.7 4 core system.


This is assuming the application will utilize all core simultaneously. if only 4 or less cores are being utilizes at one time then the 4.7 x 4 will outperform the 2.8 x 8
a c 318 à CPUs
August 24, 2011 5:19:57 PM

3xch4ng3 said:
This is assuming the application will utilize all core simultaneously. if only 4 or less cores are being utilizes at one time then the 4.7 x 4 will outperform the 2.8 x 8

True enough, my point was, that even at a utilization of 6@2.8 , the faster 4 core would be better.
!