I'm still questioning Hyperthreading/ SMT benefits

[rdgoodri]

I'm still thinking Hyperthreading/ SMT is more of a marketing move than a real benefit to gamers. If you compare performance of tasks running on one physical core vs. two virtual threads running on one core, (and splitting the cache), each virtual thread will always run slower than the thread on the dedicated physical core. However, you can run more of them. Do you agree, why or why not?

 

[kanewolf]

You have to benchmark to determine if hyperthreading will benefit. If there is enough memory access or other off-CPU interaction then hyperthreading can be more efficient.

 

[madmatt30]

I don't think it matters as much now we have 6 core mainstream cpu's.

Certainly made a big difference on the g4560 vs the older non-ht g4500.
30-40% gains in some cases.

 

[kanewolf]

I don't think it matters as much now we have 6 core mainstream cpu's.

Certainly made a big difference on the g4560 vs the older non-ht g4500.
30-40% gains in some cases.

You are limiting your thinking to gaming. I work with very large servers at work (256 cores and 2TB RAM). Everything that gets run on those servers is benchmarked to determine how many CPUs a specific algorithm can scale. Some are 8, some are 128. It just depends on how the code is written. The only way to determine if you benefit is to take specific applications and test with SMT on and SMT off.

 

[mdd1963]

How many games were benched last year year where the 7600K equaled the 7700K when both were at the same clock speed?

(It was rare, but, did sometimes happen. You want to see 'well threaded' look at BF1.

 

[gamerk316]

I'm still thinking Hyperthreading/ SMT is more of a marketing move than a real benefit to gamers. If you compare performance of tasks running on one physical core vs. two virtual threads running on one core, (and splitting the cache), each virtual thread will always run slower than the thread on the dedicated physical core. However, you can run more of them. Do you agree, why or why not?

Depends on the CPU in question. The leap from a Pentium to an i3 was HUGE because hyperthreading allowed for low-workload system threads to run on hyperthreaded cores without having to make the game you are currently using come to a complete stop to let them run.

As the number of cores increases, the benefits to gaming drops, mainly since games don't use that many threads at a time. Hyperthreading will almost always help reduce latency in any case.

 

[madmatt30]

@kanewolf - I agree but he did primarily mention gaming

@ mdd1963 - yeah bf1 is heavily multithreaded , a rare title where the ryzen 1600 does consummately beat any stock clocked i5 , even the 6 core 8400.

 

[Dunlop0078]

Even in games hyperthreading can make a difference, on 6 core 8th gen cpu's. Here is a watch dogs 2 bench with an 8600k and 8700k both at 5ghz, 8700k still comes out on top. Same story in a lot of modern titles.

 

[gamerk316]

The main advantage with all forms of SMT is you have another logical core where lighter processing workloads can be run in a way that doesn't cause a thread from an application you are currently running from coming to a complete stop. That's almost always going to give some small gain in performance simply because there are literally thousands of OS threads running in the background that don't do much work, but would otherwise cause your application to stop for a few ns every so often, which adds up over time. However, as the number of physical CPU cores increases, the benefit of SMT decreases [less likely to run into the above problem]. This is why an i3 is SIGNIFICANTLY better at gaming then a Pentium, but an i5 and i7 are generally about the same.