What REALLY, is the function of multi cores?

[S.Taylor]

Thanks!!!
I just wanted to know if i got the best computer, within reason, budget-wise, (as well as to get into the recent picture of things [it's easier to study things when you get involved a bit, like to buy something]).

[Gian-Carlo Pascutto]

Whether the software uses threads or processes doesn't make much difference in the picture that the taskmanager is giving (assuming you are talking about the 8 graphs corresponding to the 8 hyperthreads of an i7).

You'll see one process using 100% CPU (multithreaded engine), or you'll see 8 processes each using 13% CPU (multiprocessed engine).

Note that for the engines HyperThreading might as well have been called HyperProcessing - they don't care and just see extra CPUs.

[syzygy]

Whether the software uses threads or processes doesn't make much difference in the picture that the taskmanager is giving (assuming you are talking about the 8 graphs corresponding to the 8 hyperthreads of an i7).

You'll see one process using 100% CPU (multithreaded engine), or you'll see 8 processes each using 13% CPU (multiprocessed engine).

Yes, but in the 8 "CPU Usage History" graphs shows in the "Performance" tab this won't show as a difference.

Hmm, maybe Eelco's "But with hyperthreading the taskmanager can show eight threads" was not referring to those graphs but to the Process list, but there you can't see individual threads I believe.

Note that for the engines HyperThreading might as well have been called HyperProcessing - they don't care and just see extra CPUs.

One thing that is confusing is that "thread" sometimes refers to an OS thread and sometimes to a hardware thread (= a full architectural x86 processor state), and those two concepts are quite different. Thread in hyperthread refers to the latter.

[Carlos777]

Hello,

I have a Core i3, 2 real cores and 4 threads. I can't disable HT in the BIOS. So I have to use msconfig. I am not sure which are the real cores. There are 0, 1, 2 and 3. Maybe, someone could help me with it.

I am using this laptop to run 2 parallel single core engines tournaments. I read somewhere that Windows 7 can manage well the using of cores, meaning that it priorizes the use of the real cores before the logical ones.

About Core i5 (4 real cores) vs Core i7 (4 real cores with HT disabled). Isn't it better for chess to get the i5? Cheaper and has the same quantity of cores.

Best regards,
Carlos

[bob]

Hello,

I have a Core i3, 2 real cores and 4 threads. I can't disable HT in the BIOS. So I have to use msconfig. I am not sure which are the real cores. There are 0, 1, 2 and 3. Maybe, someone could help me with it.

I am using this laptop to run 2 parallel single core engines tournaments. I read somewhere that Windows 7 can manage well the using of cores, meaning that it priorizes the use of the real cores before the logical ones.

About Core i5 (4 real cores) vs Core i7 (4 real cores with HT disabled). Isn't it better for chess to get the i5? Cheaper and has the same quantity of cores.

Best regards,
Carlos

Simple answer.

1. Are you SURE you can't turn off hyper-threading? Sometimes it is called "logical CPU on/off"

2. Ignore it. If you just use two threads on the chess engine, the operating system will run those two threads on two real cores, as it should. This was not true with early versions of operating systems right after hyper-threading came out, but you can now safely ignore it. Just don't run more threads than physical cores in a chess engine and you will be good to go.

[Carlos777]

Simple answer.

1. Are you SURE you can't turn off hyper-threading? Sometimes it is called "logical CPU on/off"

There is an option in BIOS about virtualization, there is no other option in relation with disabling HT. I tried disabling this virtualization mode, but nothing happens, whether its enabled or disabled the process shows 25% in Task Manager.

2. Ignore it. If you just use two threads on the chess engine, the operating system will run those two threads on two real cores, as it should. This was not true with early versions of operating systems right after hyper-threading came out, but you can now safely ignore it. Just don't run more threads than physical cores in a chess engine and you will be good to go.

Great. As I wrote in my previous post, I am running 2 single core tournaments w/ ponder off at the same time. So, I guess its the same.

Thank you for the fast response.

Carlos