Hyperthreading and Chess Analysis

I've read many of the forum topics on hyperthreading and why, while you will get short-term kn/s gains, the overall analysis quality will suffer.

My question is this: I have a quad core machine. I want to run all 4 cores during analysis. Do I: 

a) leave hyperthreading as enabled and set the number of threads as 4 in the engine configuration 

-or-

b) turn off hyperthreading and set the number of threads as 4 in the engine configuration?

Can you also explain the idea of kn/s to me ?

Ace_Club,

Option (a is correct.

Custardgirl,

Kn/s is kilo nodes a second--the engine is looking at x thousand(kilo) positions (nodes) a second.

Good luck!

@theturk1234

Thanks for the response! Would you mind explaining, for my own curiosity, as to why option a) over option b)?

In my mind, and I may be thinking about this incorrectly, wouldn't option a) still allow for degraded performance if the computer is using one of the hyperthreads for some non-chess function? I only ask because I've tried option a) before and it results in 50% CPU usage. I would have thought that utilizing all 4 cores to analyze would have resulted in 90%-100% CPU usage. 

I have HT disabled on my octo-core, but it doesn't matter as long as you set threads = physical cores.

However, some testing recently has revealed some engines may actually receive an elo benefit if using all logical processors even if that's counterintuitive.