What is the value of logical cores ( HT) for chess ?

[Dann Corbit]

The only benefit I can think of for hyper-threading is that it allows a finer division of work load, and a way to set a box to very nearly 100% capacity without the 100% CPU utilization lockout.

So, for instance, I can set my 3970x at 63 threads going full tilt and still be able to connect remotely with mstsc.
If I had all 64 threads going, you simply cannot connect.

Or, I might want to run two different engines at the same time with 31 threads each.

That sort of thing.

But it is less efficient computationally and runs hotter.
In general, it is a bad idea for chess, but I leave HT on because other apps like database really do get benefit.
They are generally disk and memory limited rather than computationally.

[MikeB]

The only benefit I can think of for hyper-threading is that it allows a finer division of work load, and a way to set a box to very nearly 100% capacity without the 100% CPU utilization lockout.

So, for instance, I can set my 3970x at 63 threads going full tilt and still be able to connect remotely with mstsc.
If I had all 64 threads going, you simply cannot connect.

Or, I might want to run two different engines at the same time with 31 threads each.

That sort of thing.

But it is less efficient computationally and runs hotter.
In general, it is a bad idea for chess, but I leave HT on because other apps like database really do get benefit.
They are generally disk and memory limited rather than computationally.

I find myself running tests on 55 threads, keeping 8 threads around for some analysis and leaving one thread for OS. Very happy with 3970x. I have done somes tests with 15 threads ot 30 threads - its not like going from 2 threads to 4 threads - which may be a 50-60 Elo - its more like 25-30 Elo at best. And going from from 30 to 60 threads is maybe 10 Elo at best - of course threads 33 to 60 are logical cores and are much weaker than threads 1 through 32 ( i know it doesn't work exactly like that, but you can get my drift).The accountant in me still can't justify the expense of the 3990x over 3970x, an extra $2K for 30 Elo. Accountants don't get old, they just die.

[Dann Corbit]

I made the same decision over the 3970x verses the 3990x.
But when the 5 nm stuff comes out, I will be sorely tempted, especially if they have 256 cores/512 threads.
I can always run multiple engines on one box, since the added gain will be wimpy, but hey, at 512 threads that is ten engines with 50 threads.

I have seen 100M NPS with 32 threads, though that is rare. I usually get around 35-40M NPS at 32

[MikeB]

I made the same decision over the 3970x verses the 3990x.
But when the 5 nm stuff comes out, I will be sorely tempted, especially if they have 256 cores/512 threads.
I can always run multiple engines on one box, since the added gain will be wimpy, but hey, at 512 threads that is ten engines with 50 threads.

I have seen 100M NPS with 32 threads, though that is rare. I usually get around 35-40M NPS at 32

256 real cores will be fun - are you now running linux or windows?

[mwyoung]

The only benefit I can think of for hyper-threading is that it allows a finer division of work load, and a way to set a box to very nearly 100% capacity without the 100% CPU utilization lockout.

So, for instance, I can set my 3970x at 63 threads going full tilt and still be able to connect remotely with mstsc.
If I had all 64 threads going, you simply cannot connect.

Or, I might want to run two different engines at the same time with 31 threads each.

That sort of thing.

But it is less efficient computationally and runs hotter.
In general, it is a bad idea for chess, but I leave HT on because other apps like database really do get benefit.
They are generally disk and memory limited rather than computationally.

Yes you can run 64 threads. Why are you running your modern hardware old school. You don't ever need to core cut your threads with a modern OS, or hardware. Simple run the chess engine at a lower priority at 64 threads. If you running a Fritz GUI this is easy, by clicking the low priority button when you install the engine. This is why this option exist. And if you are running back ground software. The engine will give way. If needed to the demand only of the other software. And If you are not running anything else the chess engine will use all the CPU horse power automatically. And you will never waste any CPU run time. Like when you are core cutting your CPU.

[Dann Corbit]

I made the same decision over the 3970x verses the 3990x.
But when the 5 nm stuff comes out, I will be sorely tempted, especially if they have 256 cores/512 threads.
I can always run multiple engines on one box, since the added gain will be wimpy, but hey, at 512 threads that is ten engines with 50 threads.

I have seen 100M NPS with 32 threads, though that is rare. I usually get around 35-40M NPS at 32

256 real cores will be fun - are you now running linux or windows?

My old servers are all Ubuntu, but the 3970x is Windows. They did not offer a Linux version

[yurikvelo]

So, for instance, I can set my 3970x at 63 threads going full tilt and still be able to connect remotely with mstsc.
If I had all 64 threads going, you simply cannot connect.

That's true only if you intend to run tournament and need normal process priority for fair play.

If you don't run tournaments - you can go with "Idle" priority and run any number of processes or threads (>> than SMT core count)