a dual core processor at X.x speed means there are two cores working at X.x or what?

Question

when people talk about dual core processors at X.x speed do they mean that there are two cores working at X.x speed each?

If so, does this means that a solo core working at 2X.x speed is equivalent to a dual core at X.x?

Answer 1

A Dual Core processor provides about a 180% performance gain over a single core of the same speed on multi-threaded tasks (there is some overhead due to the need to manage the two cores).

On single threaded tasks there's no difference (though with a modern OS it means you can run two of them at the same time).

Answer 2

Each core of a dual-core CPU runs at the given X.x speed.

Example: A dual-core 2Ghz chip has two 2Ghz cores.

Also, it is important to remember that the fastest a single core can run is X.x, meaning:

If you're not utilizing both cores (ie multi-tasking, using software programmed for dual-cores, etc), your computer will only run at X.x (X.x being the independent speed of a single core of the duo.)

Example: If I'm running a single Internet Explorer window on my 2Ghz dual-core CPU, my computer will be working at a maximum of 2Ghz, not 4Ghz, as only one core is being utilized.