Multicore and Multithreading

[ErikJan]

I (think I) know the difference between multicore processors and multithreading. However the full impact on our modern (Win10; Skylake 6700 generation) ) PCs is not completely clear. I think that the CPU itself has some intelligence to run certain tasks in parallel (and/or even out of sequence). One can also develop software that allows parallel processing (multithreading?) but most 'normal' software still uses sort of a single threaded approach. Exceptions are rendering programs, some professional programs and games... Or am I wrong here? When looking for my new PC I learned for discussion boards that typically for non-game applications clock-speed was more important than the number of cores. Which is one of the reasons why I chose a Skylake 6700 i7; I have less cores that some other i7 CPUs but my clock speed is higher.
Recently someone told me that multicores are way better and faster as when I'm running a heavy task that takes e.g. 100% of a core, another task 'gets' the other core and can still run in parallel (a single core would have to stop the other task until the 100% task is done). I don't believe that is true but I'm confused. Let me bring the multi=threading term back in here... how does all of this fit together?
I did some searches but can't find a short and simple explanation... Anyone who can shed some light on this?

[HansV]

Many applications nowadays are multi-threading.

In recent versions of Excel, you can specify how many cores Excel will use in File > Options > Advanced > Formulas. If you have to recalculate a large worksheet with lots of formulas, Excel will distribute the calculations over the specified number of cores.

Recent versions of WinZip will use multi-threading to compress several files simultaneously, if possible.

Etcetera.

Another advantage of multiple cores is multi-tasking. Fifteen years ago or so, when I ran a virus scan, I wasn't able to do anything else on my computer: the virus scan took so much CPU power that other programs ground to a halt. Nowadays, I don't even notice if a scan is being run in the background.

So if you often run many programs simultaneously, or if you want to be able to continue working while a complication calculation takes place in the background, multiple cores do offer a significant advantage.

If you only use a single program at a time, the advantage is much less clear.

But it's a trade-off of course. There'd be little point in having 32 cores each running at 0.5 GHz. Quad-core is probably sufficient for most users, eight-core for heavy multi-taskers.

[PJ_in_FL]

... eight-core for heavy multi-taskers.

Why should my (ever increasing ) weight make a difference?

I just a GROWING lad in his 50's!

[HansV]

It puts a greater load on the CPU...

[StuartR]

Most chips have two or more processors, usually 2, 4 or possibly 8

Some chips can execute multiple threads on each CPU, this is not as good as having multiple processors, but is better than having to do a full context switch to offload one programme and onload another.