Is HyperThreading/SMT really needed?

[ehume]

I don't have a link, but I remember . . . my own benchmarking on a TR system . . .

TR?

 

[Markfw]

TR?

TR=Threadripper

 

[DominionSeraph]

Yes, because we only play todays games. /s
That's why I despise the i5.
Because it leads to extremely shortsighted thinking.
Spend the small extra money and get the i7 for the longevity.

The difference in price between an i5 2500 and an i7 2600 at launch would buy you an entire i5 2500 system now. Two i5 2500's > one i7 2600.

 

[whm1974]

The difference in price between an i5 2500 and an i7 2600 at launch would buy you an entire i5 2500 system now. Two i5 2500's > one i7 2600.

The higher cost of the i7 is the reason the i5 is more popular as the money saved can go towards a better CPU, more memory, or a SSD.

 

[Spartak]

40% is a stretch. It's more like 30%, best case, on synthetic loads.

Even then, it is most likely that just means Intel is more efficient at populating it's functional units with a single thread, which is in line with Intels better single thread IPC. What is left over for SMT/HT, are the idle units from the first thread.

30% best case, with performance varying between 0-30% that comes to ~15% boost on average, maybe a bit higher with AMD. But this 15% isn't 'free', it also means your CPU consumes close to 15% more power on average load and up to 30% with FP intensive threads.

if you arent power/heat constrained and don't run many highly parallel tasks a 4C/8T processor with higher single threaded performance will probably be a better choice than a lower clocked 6C/6T one, simply because you don't always use all those cores, but you do always use a few of them.

It's just one of the performance ingredients alongside IPC, frequency and number of cores you can play with to optimise for your specific workload and power budget. I for one plan to disable SMT on my new SFF passive rig to stay within the needed power envelope. I don't run many massively parallel tasks so it's more of a speed limiter you wont encounter a lot anyway but prevents your PC from overheating.

 

[TheELF]

150% performance increase...
1c/1t=10FPS

1c/2t=25FPS...

 

[itsmydamnation]

40% is a stretch. It's more like 30%, best case, on synthetic loads.

Even then, it is most likely that just means Intel is more efficient at populating it's functional units with a single thread, which is in line with Intels better single thread IPC. What is left over for SMT/HT, are the idle units from the first thread.

Unlikely, the SMT advantage stays when you increase the memory clock on Zen while also closing the single thread perf gap. SMT oooe cores are generally going to be load store limited, both cores have the same 2l/1s. What Zen has over skylake in this regard is slightly wider issue/retirement. If Zen had more l/s then this advantage would be more pronounced but given the l/s bottleneck it only helps to fill bubbles( Michael Clarke talks about this in the Zen hotchips presentation)

 

[tential]

The higher cost of the i7 is the reason the i5 is more popular as the money saved can go towards a better CPU, more memory, or a SSD.

And you'll have to upgrade the i5 faster. Instead of paying $100 extra for an i7 you'll pay more to upgrade your i5 earlier, pay for a new mobo, and a new ram standard....

The i7 is just better all around.

 

[whm1974]

And you'll have to upgrade the i5 faster. Instead of paying $100 extra for an i7 you'll pay more to upgrade your i5 earlier, pay for a new mobo, and a new ram standard....

The i7 is just better all around.

In the next two to three years or so I will likely be building a new rig with an 8 core CPU or maybe with more cores.

 

[tential]

In the next two to three years or so I will likely be building a new rig with an 8 core CPU or maybe with more cores.

If you can wait, wait. Nothing is pressing for a Haswell owner. Haswell to me is the cut off. Once you have a Haswell or newer system... just stick with it as long as you can and spend your money on GPUs.

Also, you get the benefit of seeing whether AMD can overtake intel in ST performance with Ryzen 3rd gen or not or at least make a compelling offer for the best gaming CPU.

 

[TheELF]

Also, you get the benefit of seeing whether AMD can overtake intel in ST performance with Ryzen 3rd gen or not or at least make a compelling offer for the best gaming CPU.

Yeah right,it's 10-15% now not including the 20-25% core clock difference,so 30-40% difference all in all,good luck with that...

Also for a gaming CPU the "creativity" benches are irrelevant,it's close to 50% difference even with similar clocks .
https://www.youtube.com/watch?v=olI9Mmtw39Y&t=216s

And yes, it does translate to multithreaded games as well,ryzen needs double the threads to just get close to halve the threads on intel.
https://www.youtube.com/watch?v=ucJqHUpc2RU&feature=youtu.be&t=375

 

[whm1974]

I'm thinking with AMD getting more competitive, SMT/HyperThreading will be a standard feature by the time I do a new build anyway so this would a rather moot question by then.

Agree, disagree?

 

[Markfw]

Yeah right,it's 10-15% now not including the 20-25% core clock difference,so 30-40% difference all in all,good luck with that...

Also for a gaming CPU the "creativity" benches are irrelevant,it's close to 50% difference even with similar clocks .
https://www.youtube.com/watch?v=olI9Mmtw39Y&t=216s

And yes, it does translate to multithreaded games as well,ryzen needs double the threads to just get close to halve the threads on intel.
https://www.youtube.com/watch?v=ucJqHUpc2RU&feature=youtu.be&t=375

This has nothing to do with SMT and HT. If you want to compare, run a benchmark on an Intel processor that is CPU dependant with HT OFF. Then turn HT on, and run the same benchmark. Calculate how much more work it did.

Then do the exact same think on an AMD Ryzen.

Then see which got more performance out of their respective HT/SMT uplift.

 

[tential]

This has nothing to do with SMT and HT. If you want to compare, run a benchmark on an Intel processor that is CPU dependant with HT OFF. Then turn HT on, and run the same benchmark. Calculate how much more work it did.

Then do the exact same think on an AMD Ryzen.

Then see which got more performance out of their respective HT/SMT uplift.

This doesn't begin to get into the weird ways some games scale with HT/SMT. Especially with SMT, since it's newer and requires Windows as well as everyone else to catch up with it.
I think HT had similar growing pains but now is usually always a performance uplift.

When SMT is always a performance uplift in games, that will be a great time for AMD. Right now, SMT can hurt AMD some times, which is extremely unfortunate.

 

[Markfw]

This doesn't begin to get into the weird ways some games scale with HT/SMT. Especially with SMT, since it's newer and requires Windows as well as everyone else to catch up with it.
I think HT had similar growing pains but now is usually always a performance uplift.

When SMT is always a performance uplift in games, that will be a great time for AMD. Right now, SMT can hurt AMD some times, which is extremely unfortunate.

I don't know about that, its just the methodology in the post I quoted had nothing to do with evaluating this.

 

[tential]

Delete Post.

 

[Spartak]

I don't know about that, its just the methodology in the post I quoted had nothing to do with evaluating this.

Especially when you compare it in a situation where the system dives under a critical threshhold for performance.

---> Hey! When I use both my legs I can run 6 times as fast compared to limping on one leg. Hence, doubling your legs will give you six times the performance