Why does a conversion thread never use more than 25% of CPU?

[HarryT]

My rather elderly laptop has a dual-core i5 processor (state of the art when I bought it many years ago ), and I notice that, when I convert books, even if there's only one "calibre-parallel" conversion thread running, Windows Task Manager shows that the conversion thread never exceeds 25% CPU usage.

At first I thought that this meant that it was running one CPU core flat out but, given that I have a dual- rather than a quad-core CPU, this is not the case; it's never running a CPU core at more than 50% capacity.

Is this a limit imposed by Calibre itself (or its library) or is it something to do with my PC? I ask merely out of curiosity.

Thanks,

[pdurrant]

Perhaps your laptop processor has HyperThreading, which makes each core look like two.

[HarryT]

Thanks - that makes sense!

[theducks]

Originally Posted by HarryT

Thanks - that makes sense!

Harry
Check your BIOS settings, you may have an option to turn off CPU Hyperthreading, leaving the whole core to Calibre (50%).

But if nothing else is seriously competing for that core, there is probably not a noticeable performance gain

[HarryT]

Thanks!

I actually prefer it the way it is, because conversion of large files is something I generally do as a background activity, and the way it is now, the three conversion threads use at most 75% of the CPU, leaving my PC responsive for doing other things. My question was, as I said, prompted by nothing other than curiosity.

[theducks]

Originally Posted by HarryT

Thanks!

IMy question was, as I said, prompted by nothing other than curiosity.

As long as it does not end up like the proverbial Cat