How hard you can work a CPU is highly dependent on the type of CPU and the type of work it is doing, there is no one size fits all number for how hard to work them.
Newer = more capable - Newer CPUs have larger on-chip cache memory, allowing more instructions to be kept nearer the cores. Cache memory is quicker to access than main memory but there is much less of it Megabytes of very fast cache, Gigabytes of fast ram and Terabytes of slow disk.
It’s also not just about the speed of the clock – a 3.4 GHz Pentium IV is nowhere near as capable (as in “can get through work”) as a brand new 2 GHz Xeon processor. Because the newer CPU can do more in one clock cycle then a older CPU can do in many.
More cores = can be pushed harder - It’s all about THROUGHPUT, not just speed.
The more cores a CPU has the harder you can run it without performance problems.
Dependent on the type of work; hyper-threading or not…
Some best practice recommendations are:
· At 50% busy will take twice as long as if it were 0% busy.
· At 80% busy it will take 5 times as long.
· At 90% it will take 10 times as long.
You can see with one core it does not take much work to make throughput slowdown.
· At 50% it will take 1.3 times as long.
· At 80% it will take 2.7 times as long.
· At 90% it will take 5.2 times as long.
• 50% - 1x, 80% - 1.02x, 90% - 1.22x
For a 16 core CPU it does not make much of a difference running it at 80% compared to 50%. But you have to keep in mind that all configurations max out at 100% just the number of cores flattens out the curve. You can see with more cores it takes longer to hit the knee of the curve.
Benefits of Multiple Cores
This chart illustrates that as you add more and more cores the response time curve is more and more flat.