Do games use hyperthreading?

[futurefields]

I just put together and new system and ordered it couple days ago. I went with an i7 because I figured more threads since newer games will probably use them. BUt then I check some benchmarks and it looks like i5's are still keeping pace with i7's (and in some cases beating them? I guess because of HT latency eek)

Did I make the right choice with the i7? Maybe in the future more games will use the hyperthreading? Or do games really need the physical core? Hyperthreading is no good in this case?

 

[PeterScott]

If a game can benefit significantly from more real cores, chances are it can also benefit, but less significantly from HT.

Remember though that HT only takes advantage of idle execution units in a CPU, and for Intel that idle seems to max out around 20%.

That would be a 20% improvement from HT if a game was perfectly parallel, and had no GPU bottleneck at all, so just about never, so expect less than that.

2 more real cores OTOH might have 50% improvement maximum in again perfect theoretical circumstances, so expect less than that.

In a typical game that might be more like 5% for HT and 10% for 2 more real cores, or close to zero gains for both depending on the game.

 

[Excessi0n]

Games may or may not take advantage of the extra threads, but background tasks can make use of them even if games don't directly benefit. So if you leave things running in the background, or windows decides to do something, or whatever, it's less likely to interrupt the threads being used for the game. That should result in a smoother experience on the i7 even if the average FPS isn't much different.

Or at least that's what used to be the case. Don't know if the new six-core chips change things since I haven't seen any frametime comparisons.

 

[TheELF]

If a game can benefit significantly from more real cores, chances are it can also benefit, but less significantly from HT.

True

Remember though that HT only takes advantage of idle execution units in a CPU, and for Intel that idle seems to max out around 20%.

It's 20-25% for sandy/ivy but only for distributed computing software like cinebench and so on,for haswell and later it's around 30-35%.
Games are not as demanding and leave A LOT more resources untapped,80-90% gains for dual cores +HTT against straight dual cores is pretty much the norm.

That would be a 20% improvement from HT if a game was perfectly parallel, and had no GPU bottleneck at all, so just about never, so expect less than that.

That's the problem with the quad +HTT any modern card already get's pretty much fully utilized by 4 plain cores so the HTT can't make much of a difference.

 

[itsmydamnation]

the most scares resource to a core is load + store bandwidth, if data has poor prefetch/predict and stalls alot then it is the prime use case for HT.

 

[gregoryvg]

I've noticed in a lot of gaming benchmarks the i5 8600k (6c/6t) and i7 7700k (4c/8t) are running neck and neck, with the 7700k usually edging out the 8600k. And both are faster than the i5 7600k (4c/4t). So I would say that yes, games benefit from hyperthreading.

 

[PeterScott]

I've noticed in a lot of gaming benchmarks the i5 8600k (6c/6t) and i7 7700k (4c/8t) are running neck and neck, with the 7700k usually edging out the 8600k. And both are faster than the i5 7600k (4c/4t). So I would say that yes, games benefit from hyperthreading.

I doubt that for equal clock speeds. At equal clocks, I expect the 8600K would edge out the 7700K. Real cores are better than HT.

 

[rvborgh]

i would think that for games you would want your main simulation thread (ie the one that bottlenecks the game) to be run on a non hyperthreaded core if possible (ie keep other threads off the associated logical core that matches that - say core 1). Run everything else on the hyperthreaded cores. Process Lasso would be useful for this.

 

[CropDuster]

In some games like Battlefield and R6 Siege I would notice some stuttering with HT thread on, so I would generally leave it off when gaming. Max FPS would be lower but it seemed like smoother gameplay.