What is the number of "CPU" next to each engine's name in engines rating list? And is my computer 1CPU, 2CPU or 4CPU? Look at this engine rating list which compares all the versions of Stockfish.

After the name of each engine we can see one of these three things:


4CPU
2CPU
Nothing, which probably means: 1CPU


And it seems that the same engine is stronger by roughly 80 Elo when run on 4CPU instead of 1CPU.

I'm not exactly sure what the number of "CPU" is... Is it related to the number of cores?

I would like to know if my computer is 1CPU, 2CPU or 4CPU.

Here is the specifications of my computer (which I found in Control Panel\System and Security\System):


Alienware M18x
Windows 8.1
Processor: Intel(R) Core(TM) i7-3740QM CPU @ 2.70 GHz 2.70 GHz
Installed memory (RAM): 16.0 GB
System type: 64-bit operating system, x64-based processor


So is my computer 1CPU, 2CPU or 4CPU ?
Before multicore processors, if you saw something like 4 CPUs they would be referring to a chess engine running on a computer that had a motherboard that actually had 4 separate processors on it. Now, they they could be referring to multicore processors. For example, your i7 is a quad-core processor with 4 processor cores. It's like 4 processors in 1 package.

It's hard to say for sure which one it is, because even after reading their testing information in the about page, etc. They do not make clarifications about the actual hardware it is running on.

This is all I could find: 


  Should be set to the same value of either 128 or 256 MB for all engines in a match or tourney. There are two exeptions: 1) Engines using 2 CPUs should have double hash size, compared to single-CPU engines in the same tourney. 4-CPU engines should have 4 times amount of hash. 2) Smaller hash size can be used if an engine has problems with particular hash size, or if it does not allow to configure hash size.