I first asked this question at cstheory, but they suggested to ask my question here, so here it goes ...
I'm working on my masters thesis and I need to have theoretical value of the (average) speed gain that a quadcore processor brings compared to a singlecore processor, when they both use the same frequency. So for example the speed gain of a 2 GHz singlecore vs. 2 Ghz quadcore.
Somewhere on the internet I've read that a quadcore is 2.6 times faster than singlecore, but the author didn't mention any source so I cannot use that in my thesis.
I've been trying to calculate some things myself, but didn't come to a conclusion. I tried like this:
threads | quad core | single core | ratio --------|-----------|-------------|------- 1 | 1 | 1 | 1 2 | 2 | 1/2 | 4 3 | 3 | 1/3 | 9 4 | 4 | 1/4 | 16 5 | 3+1/2 | 1/5 | 17.5 6 | 2+2(1/2) | 1/5 | 15 7 | 1+3(1/2) | 1/5 | 12.5 ...
This table represents the timeslices available to execute a task (I've taken a fair 50/50 usage for each thread). For example when using a singlecore and a application uses 3 threads, each thread can work 1/3 of the time, while with a quadcore each thread can work 100% of the time, because 3 threads can be spread accross a separate core. After playing with some calculations in Excel, I could not come to any conclusion.
I'm a bit stuck and need some fresh ideas on how to get a theoretical number that represents how much faster a quad core is (on average) compared to a single core. Maybe some of you know some empirical numbers with a good reference to the source? Anyway, all the help is welcome, because I'm a bit stuck and this is the last part I need to cover in my thesis.