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Leaked Benchmarks Suggest Intel Will Drop Hyperthreading From Core i7 Chips (arstechnica.com)
According to leaked benchmarks found in the SiSoft Sandra database, there is an Intel Core i7-9700K processor that doesn't appear to have hyperthreading available. "This increases the core count from the current six cores in the 8th generation Coffee Lake parts to eight cores, but, even though it's an i7 chip, it doesn't appear to have hyperthreading available," reports Ars Technica. "It's base clock speed is 3.6GHz, peak turbo is 4.9GHz, and it has 12MB cache. The price is expected to be around the same $350 level as the current top-end i7s." From the report: For the chip that will sit above the i7-9700K in the product lineup, Intel is extending the use of its i9 branding, initially reserved for the X-series High-End Desktop Platform. The i9-9900K will be an eight-core, 16-thread processor. This bumps the cache up to 16MB and the peak turbo up to 5GHz -- and the price up to an expected $450. Below the i7s will be i5s with six cores and six threads and below them, i3s with four cores and four threads. Even without hyperthreading, the new i7s should be faster than old i7s. A part with eight cores is going to be faster than the four-core/eight-thread chips of a couple of generations ago and should in general also be faster than the six-core/12-thread 8th generation chips. Peak clock speeds are pushed slightly higher than they were for the 8th generation chips, too.
workloads that cause a lot of switching between processes/Jobs. We have many systems that benefit hugely from hyper threading, others that get bugger all and still more where we explicitly disable it as it slows down the system.
Integer heavy workloads, sometimes branch heavy coding. The physical core 0 really can do two things at once, but only for some things. Much like how you can pet two cats in half the time with your two hands, but can only drink water at a rate limited by your mouth.
The big things are this:
1- It is rare to find a workload that works better with HT off
2- It is common to find a workload that gets some speedup
3- HT may have some vague security issues, based on recent actions from BSD etc. Maybe.
Anyway, those three things should mostly determine whether you turn HT on or off on your box, and really just the first two unless you are Server Guy.
So to recap the 8th gen of Intel. The i7 had the most cores at six with HT enabled. i5 was just like the i7 but with HT turned off. The i3 had HT in gen 7 so it was two cores/four threads, in 8th gen they gave it two more cores and turned off HT. So: i7=6/12, i5=6/6, i3=4/4. The i9 in gen 8 was really weird. The clock would scale down the more cores you used, it was very odd and minus the fact that the 18 core version was roughly the price of a used car, it was expensive. The price per performance with the i9 was incredibly low. A 3.4 Ghz i7 would give you a better CPU mark / $ by almost 200%, not to mention that an AMD six core FX-6300 would give you better CPU mark/$ by almost 800%. So clearly the i9 wasn't going to win you an award for price sensitive consumers.
So all that said, and this is my opinion so it's literally worth whatever value you choose to give it, I think Intel is going to reposition the line up to disable HT on all "consumer" processors and focus on just keeping HT and "pro" features in the i9. I personally think it's a back hand to Intel consumers, but I'm an AMD fanboy so full disclosure there. But yeah, I think the i3, i5, and i7 are all going to eventually be labelled as the "cheapy", "actual desktop", "gamer" CPUs in that order and the i9 is going to be viewed as "workstation" and thus the i9 isn't going to focus on price/performance balance. So, i3 will be 4/4, i5 will be 6/6, and i7 will be 8/8 with the i9 being whatever crazy numbers they throw at the chips with hopefully not any of that weird scaling core/HT/Ghz stuff.
That's just my hot take on this, open to hear what others think.
If this is how they plan to deal with the Spectre/Meltdown issues permanently, I'm ok with that.
HT has nothing to do with that issue. That's part of the instruction pipeline within the CPU. The core of it is a thing called speculative execution, where a CPU goes and fetches things before the actual instruction hits the core. The true fix will be to detect unprivileged instructions in the pipe (because actually getting rid of the pipe is *NOT* ever going to be an option) and then act on that.
And the end of the day, if I can still play my games, I really don't care what's inside that hunk of silicon, as long as my games still work as good as they always have.
Yeah I think that's ultimately what matters most here so I wouldn't worry too much about it anyway, just stay up to date on patches, which I'm sure you do.
spectre related attacks rely on speculative execution. hyperthreading is not speculative execution.
There are plenty of CPU's vulnerable to spectre attacks that have no hyperthreading capability. turning it off on your Intel CPU doesn't mitigate it either.
anyone who cares tests to see if they are in one of the fringe cases that gets worse performance. Far more likely to either have no effect on performance or a slight increase.
It made a big difference on WinXP with single-core CPUs because XP had lots of performance chokepoints that were limited to a single thread per "CPU".
The name resolver (which handled not only DNS lookups, but drive-path resolution for Explorer as well) is a noteworthy example. If the browser triggered a "bad" DNS lookup, it would hang Explorer (including the Start menu) until the DNS lookup timed out (30-90 seconds later, IIRC).
Hyperthreading mitigated 99% of that, because even if one name resolver thread got hung up, the other could keep chugging along.
As of Win10, most of those chokepoints are gone, and HT is useful mainly with virtual machines (by simplifying program logic since each virtual core gets its own set of registers). The catch is, recently-documented security vulnerabilities suggest it can be used to leak info between VMs... a minor issue for someone using a VM to run Linux under Windows for convenience, but a potentially HUGE issue for comercial hosting services w/multiple unrelated customers.
In any case, HT is a huge benefit with one single-core CPU, but offers little if you have 8 cores to begin with.