Question 1151 Cores vs. Hyperthreading?

Titanion

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In practical terms, lets say gaming and then video editing, what is the difference between having 6 cores and hyperthreading (8700K) vs. 8 cores and no hyperthreading (9700K)? I read a lot of people felt a little ripped off when they got a 9700K with no hyperthreading.

And then you have the 9900K with both?

Thanks
 
In a very general 'rule of thumb' it has been said that hyperthreads are roughly equivalent to 1/2 a core. It isn't a direct comparison with different generations due to improved IPC and such.
 
if you have the work for the pc to do, then more physical cores is the better idea.

hyper threading is simply a way of ensuring a core has no down time waiting to be told what to do. it is not a replacement for atrue extra physical core.

there is obviously a performance increase with hyper threading but it can't replace an extra true core.

so 8 cores is better than 6 cores with hyperthreading if you have enough work for the 8 cores to do
 
In practical terms, lets say gaming and then video editing, what is the difference between having 6 cores and hyperthreading (8700K) vs. 8 cores and no hyperthreading (9700K)? I read a lot of people felt a little ripped off when they got a 9700K with no hyperthreading.

And then you have the 9900K with both?

Thanks
The difference is that the 6 core with HTT can run 12 things at any given time while the 8 core can only run 8 things at any given time.
If the threads are relatively light they do run at full speed on hyperthreading turning it into 12 core system, if the threads are very heavy then hyperthreading only adds 15-30% which still comes close to the 8 full cores, it's win some lose some in heavy multithreading between the 8700 and the 9700 which makes the 8700 the better overall CPU because it will be much better in running many things at once that are lighter threaded.
The 9700 will only be better in very heavy multithreading.

 
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Hyperthreading is the ability of a single core to split it's bandwidth into 2 possible parallel threads. So if running a game purely, with no outside other requirements, that has a use for 7 threads, the game would use 5 cores wholey and 1 core hyperthreaded. If, however, the bandwidth used by a single thread is much larger than 50%ish, you'd end up with that particular core being single thread, not hyperthreaded.

In general, a core is stronger than a hyperthreaded core because there's no need for a scheduler to divide the core, which reduces lag. A hyperthreaded core only has an advantage when the bandwidth used by either/both threads is less than 50%ish, becoming in affect 2 individual cores.

Because games are not pure, there's windows, background tasks etc, that 7 thread game will be using almost all hyperthreaded cores, or even single core status if the bandwidth is large enough, so many instructions will be waiting for core availability. With the 9700k, you'll get that to a lesser degree, coupled with the increased IPC, makes the 9700k stronger in more areas, less lag overall, higher fps.
 
What a core with HyperThreading, or more generically, simultaneous multithreading (SMT), does is if a CPU core has spare execution resources when one thread is committed to it, another thread can squeeze in and take the spares. To put it in another way, say you have a toolbox. You don't need every tool in there for a particular job, but someone else might need what you didn't use for theirs.

Another aspect that SMT can provide is since another thread is occupying the CPU core, if the primary thread is stalled for some reason and the secondary thread can run, then there's almost no voids in the execution pipeline.

In general, it's usually better to have more cores than to rely on SMT, since SMT requires specific workloads to see a decent enough benefit.
 
One way to see the impact is to look up the passmark performance numbers.
The I7-8700K has 12 dispatchable threads that when fully occupied gives a performance score of 13742
The single thread performance rating is 2748.

By comparison, the i7-9700K has 8 threads and a rating of 14651/2909
The performance differences between the two are not great.
For that matter, the I9-9900K with 16 threads has a rating of 18823/2970. Better only if one can saturate all 16threads.