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Vhalidictes · Fri Oct 06, 2017 1:21 pm

Krogoth wrote:
Outside of a few outliers, going beyond four threads yields little or no benefits to mainstream workloads and games. Unless you plan on streaming with the CPUs. It is them main reason why Intel never bother making a 6 core normal desktop SKU until pressure from Ryzen 7.

That's true, Krogoth, but not terribly relevant. I can't recall the last time I closed down Chrome (and its attendant 20 tabs), my email client, my chat client, and all fourteen online store apps before starting up a game.

Sure, those threads won't all be active, but it's unlikely that all four cores of a 4C system will be completely free for the active game.

Topinio · Fri Oct 06, 2017 2:40 pm

Vhalidictes wrote:
Sure, those threads won't all be active, but it's unlikely that all four cores of a 4C system will be completely free for the active game.

This ++, it's not even the thread, 4C is too few now. My Xeon E3-1270 v5 (= between a Core i7-6700 and a i7-6700K) rocked when new 16 months ago, now it's a noticible limitation

Krogoth · Fri Oct 06, 2017 6:05 pm

Topinio wrote:
Vhalidictes wrote:
Sure, those threads won't all be active, but it's unlikely that all four cores of a 4C system will be completely free for the active game.

This ++, it's not even the thread, 4C is too few now. My Xeon E3-1270 v5 (= between a Core i7-6700 and a i7-6700K) rocked when new 16 months ago, now it's a noticible limitation

4 cores is plenty of go around for mainstream and gaming workloads unless you are a power user that likes to multi-task, but chances are that probably already running a HEDT-tier chip.

NovusBogus · Fri Oct 06, 2017 8:05 pm

Vhalidictes wrote:
Krogoth wrote:
Outside of a few outliers, going beyond four threads yields little or no benefits to mainstream workloads and games. Unless you plan on streaming with the CPUs. It is them main reason why Intel never bother making a 6 core normal desktop SKU until pressure from Ryzen 7.

That's true, Krogoth, but not terribly relevant. I can't recall the last time I closed down Chrome (and its attendant 20 tabs), my email client, my chat client, and all fourteen online store apps before starting up a game.

Sure, those threads won't all be active, but it's unlikely that all four cores of a 4C system will be completely free for the active game.

Yeesh...I can't remember the last time I had 20 browser tabs, an email client, a chat client, and all fourteen online store apps open in the first place! If I had even half of that going on, I'd be far too confused to even think about playing a game.

Airmantharp · Fri Oct 06, 2017 8:39 pm

Krogoth wrote:
Airmantharp wrote:
Krogoth wrote:
8350k is a sleeper in its price range. AMD has nothing that can compete against it 4 threads or lower. It should OC like a champ.

The extra two cores from its 7350k predecessor makes all of the difference.

Now this one we can agree on .

However, I would caution against using it as a gaming CPU vs. the 8600k unless absolutely price-limited: having four non-HT cores is still a limitation for real-world and/or multiplayer gaming the same as it has been since about the release of the 4000-series, as HT helps keep maximum frametimes down by providing non-FPU resources to all of the other stuff that's running on a real desktop.

Outside of a few outliers, going beyond four threads yields little or no benefits to mainstream workloads and games. Unless you plan on streaming with the CPUs. It is them main reason why Intel never bother making a 6 core normal desktop SKU until pressure from Ryzen 7.

Uh, what? Smoother gameplay is 'little to no'? Faster rendering times for photo and video editing?

Krogoth · Sat Oct 07, 2017 4:03 pm

Airmantharp wrote:
Krogoth wrote:
Airmantharp wrote:

Now this one we can agree on .

However, I would caution against using it as a gaming CPU vs. the 8600k unless absolutely price-limited: having four non-HT cores is still a limitation for real-world and/or multiplayer gaming the same as it has been since about the release of the 4000-series, as HT helps keep maximum frametimes down by providing non-FPU resources to all of the other stuff that's running on a real desktop.

Outside of a few outliers, going beyond four threads yields little or no benefits to mainstream workloads and games. Unless you plan on streaming with the CPUs. It is them main reason why Intel never bother making a 6 core normal desktop SKU until pressure from Ryzen 7.

Uh, what? Smoother gameplay is 'little to no'? Faster rendering times for photo and video editing?

The majority of gaming titles only use one or two threads at most. The third thread is barely used if at all (typically audio stuff). Photo editing is typically I/O limited not CPU-limited unless you are using a solid-state NVMe drive of some kind. Video-editing = streaming. The users who typically deal with this stuff are already on the 6-thread bandwagon and beyond.

Quad-core SKUs are still quite sufficient for the overwhelming majority of games and mainstream-tier workloads, again it is the main reason why Intel never bother going beyond it for mainsteam SKUs until Ryzen 5 and 7 came out.

HERETIC · Sat Oct 07, 2017 11:33 pm

Krogoth wrote:
Airmantharp wrote:
Krogoth wrote:

Outside of a few outliers, going beyond four threads yields little or no benefits to mainstream workloads and games. Unless you plan on streaming with the CPUs. It is them main reason why Intel never bother making a 6 core normal desktop SKU until pressure from Ryzen 7.

Uh, what? Smoother gameplay is 'little to no'? Faster rendering times for photo and video editing?

The majority of gaming titles only use one or two threads at most. The third thread is barely used if at all (typically audio stuff). Photo editing is typically I/O limited not CPU-limited unless you are using a solid-state NVMe drive of some kind. Video-editing = streaming. The users who typically deal with this stuff are already on the 6-thread bandwagon and beyond.

Quad-core SKUs are still quite sufficient for the overwhelming majority of games and mainstream-tier workloads, again it is the main reason why Intel never bother going beyond it for mainsteam SKUs until Ryzen 5 and 7 came out.

"sufficient"-yes.Optimal???
Pre W10 I tend to agree, but it seems today you need a xtra core to handle all the cr@p W10 is doing in the background-when you don't want it to.

Topinio · Sun Oct 08, 2017 3:47 am

Krogoth wrote:
4 cores is plenty of go around for mainstream and gaming workloads unless you are a power user that likes to multi-task, but chances are that probably already running a HEDT-tier chip.

Possibly, if it's a single-user system and when you're gaming you're doing little else. If the machine is Windows 10 and is multitasking, even in the background, games can suffer with 4C8T now.

Mine's a multiuser machine, 3-4 people signed in at a time (switched users) all of them multitasking. The CPU is only a desktop one, not HEDT, because the Intel market death-grip in 2016 when my i7-960 system stopped wanting to play: ignoring the AMD FX-8370 at that point in its lifecycle meant 6C+ was Broadwell-E/-EP, and the starting point in that range for 6C was either Core i7-6800K (only £80 more, but meant getting a lower quality motherboard, and it didn't even support ECC) or Xeon E5-1650 v4 (£220 more, nearly double, plus a more expensive motherboard) IIRC. :evil:

Krogoth · Sun Oct 08, 2017 1:44 pm

HERETIC wrote:
Krogoth wrote:
Airmantharp wrote:

Uh, what? Smoother gameplay is 'little to no'? Faster rendering times for photo and video editing?

The majority of gaming titles only use one or two threads at most. The third thread is barely used if at all (typically audio stuff). Photo editing is typically I/O limited not CPU-limited unless you are using a solid-state NVMe drive of some kind. Video-editing = streaming. The users who typically deal with this stuff are already on the 6-thread bandwagon and beyond.

Quad-core SKUs are still quite sufficient for the overwhelming majority of games and mainstream-tier workloads, again it is the main reason why Intel never bother going beyond it for mainsteam SKUs until Ryzen 5 and 7 came out.

"sufficient"-yes.Optimal???
Pre W10 I tend to agree, but it seems today you need a xtra core to handle all the cr@p W10 is doing in the background-when you don't want it to.

I'm on Windows 10 with signature system, and I don't have any of these "alleged" issues. The only noticeable bottleneck/hic-ups from I/O throughput on my HDDs. It seems people have already forgotten what life was like multi-tasking on a single-core system. Quad-core systems as smooth as a baby's behind for overwhelming majority of desktop users and games out there.

dashbarron · Wed Oct 11, 2017 6:51 am

8700k!

I think it's time to put my Q9450 to bed and get a new machine. I've been waiting for some sort of thread bump

cynan · Wed Oct 11, 2017 8:01 am

dashbarron wrote:
8700k!

I think it's time to put my Q9450 to bed and get a new machine. I've been waiting for some sort of thread bump

Then you really missed your chance all these years since the 3930k

Speaking off, what sort of gaming performance increase would you get with an 8700k over something like an old 3930k/60x?

ludi · Wed Oct 11, 2017 12:56 pm

dashbarron wrote:
I think it's time to put my Q9450 to bed and get a new machine. I've been waiting for some sort of thread bump

Still a very useful and relatively cool-running CPU after all these years. I just recently decommissioned a Q9450-based Dell from HTPC duty and it wasn't because it was slow.

Topinio · Wed Oct 11, 2017 1:25 pm

cynan wrote:
dashbarron wrote:
8700k!

I think it's time to put my Q9450 to bed and get a new machine. I've been waiting for some sort of thread bump

Then you really missed your chance all these years since the 3930k

Eh, what? Core i7-980X in Q1'10, 2 years after that Core 2 Q9450 and 18 months before the i7-3930K. :wink:

cynan wrote:
Speaking off, what sort of gaming performance increase would you get with an 8700k over something like an old 3930k/60x?

+50-90% I'd guess.

(Not a bad guess, just double-checked myself and a conservative +5% IPC per generation running at the respective base frequencies equals +47.6% while at +10% per generation and at the 1T turbo frequncies equals +99.2% )

Chrispy_ · Wed Oct 11, 2017 1:35 pm

Well, at 1080p with an overkill card perhaps, but the thing that stops me from upgrading my old Haswell i7 is the fact I'm almost always GPU limited.

3960X is basically a 6-core 2600K, right? That's not too shabby in a GPU-bound scenario, since all the tests where the old 2600K tanks are because they're heavily threaded and the 2600K is only a quad core.

Voldenuit · Wed Oct 11, 2017 2:15 pm

Going from a i5 4670K (4C/4T) to an i7 4790K (4C/8T) noticeably improved minimum framerates in Overwatch for me. I was running capped at 140 fps on a 1080Ti and would get dips to 100-110 semi-frequently on the i5. The i7 on the other hand was rock-solid at the 140 fps cap and almost never dipped below that, and when it did, the dips were usually around the 120-130 mark. Granted, the two chips are running at different clockspeeds (3.9 GHz on the i5 4670K vs 4.5 on the i7 4790K), but I get the impression that the added smoothness was not due to the extra clockspeed, since there's only a 15% clock speed delta.

Heroes of the Storm, on the other hand, absolutely hates the i7. I was getting solid 120 fps on the i5, but the i7 framerate graph is all over the place. The average still seems to work out to about 120 fps, but it looks like a seismograph in an earthquake instead of a straight line. This could be a case of an old game engine that was never made to core-park properly.

EDIT: worth noting that I do multitask while gaming. IRC, Discord, file transfer apps, maybe a browser window up when I'm playing Heroes as I don't have the build tree for every single hero memorized.

synthtel2 · Wed Oct 11, 2017 3:45 pm

Krogoth wrote:
The majority of gaming titles only use one or two threads at most. The third thread is barely used if at all (typically audio stuff).

Dude, no. We've been over this. That was a common architecture for 7th-gen consoles, but you can't get performance beyond "toaster" out of 8th-gen consoles by doing that, so hardly anyone is. We are not and have never been so rushed that we as an industry would be willing to leave that much CPU performance on the table. Your persistence in thinking game devs are all that clueless/lazy/rushed is getting a bit insulting.

Did you read TR's 8700K review?

dashbarron · Wed Oct 11, 2017 4:48 pm

ludi wrote:
dashbarron wrote:
I think it's time to put my Q9450 to bed and get a new machine. I've been waiting for some sort of thread bump

Still a very useful and relatively cool-running CPU after all these years. I just recently decommissioned a Q9450-based Dell from HTPC duty and it wasn't because it was slow.

I mean, it's not a slug...but I think it's a combination of too many tasks and aging (literally) hardware and heat.

Having the old browser open, a few applications and things really lag. Moving between internet windows gives noticeable pauses. A 12 year old game that should be fluid as can be can have random FPS spikes, coupled with a taxing browser and other things trying to hum quietly in the background.

The EVGA 780i I think is part of the problem. One ATA doesn't work, along with 2 other SATAs. The CPU Fan port went out about a year and a half ago (no CPU cooling for me

). Sound card went belly up. Random RAM errors on occasion keep cropping up. Only a blue screen once a month or so. And the normal couple of harddrives that started giving me weird boot issues even when they didn't contain the OS, so I've disabled 2 and one completely died.

All and all, not a bad run. About $3500 total I've spent over a decade, I think. Tinkering and playing.

Krogoth · Thu Oct 12, 2017 6:19 pm

synthtel2 wrote:
Krogoth wrote:
The majority of gaming titles only use one or two threads at most. The third thread is barely used if at all (typically audio stuff).

Dude, no. We've been over this. That was a common architecture for 7th-gen consoles, but you can't get performance beyond "toaster" out of 8th-gen consoles by doing that, so hardly anyone is. We are not and have never been so rushed that we as an industry would be willing to leave that much CPU performance on the table. Your persistence in thinking game devs are all that clueless/lazy/rushed is getting a bit insulting.

Did you read TR's 8700K review?

I did read the review and it doesn't change the notion at all.

Gaming consoles =! PCs

The majority of the games and mainstream content on the PC are still single and dual-thread at best with a few outliers go beyond that. You are lucky to find something that effectively utilizes more than four threads. It will likely not change anytime soon either because frankly coding multi-threaded software that isn't hilariously parallel is hard and time consuming. The curve is much easier on console because the platform and software platform are predictable. The PC platform isn't nearly as fortunate. It is the main reason why HEDT CPUs aren't really "faster" at gaming and mainstream then their lesser "desktop/laptop" brethren.

The killer app for multi-core CPUs for gaming needs isn't gaming itself. It is CPU video-streaming but even then you only need a six to eight core chips from either vendor to satiate that need.

Airmantharp · Thu Oct 12, 2017 11:33 pm

Krogoth wrote:
The majority of the games and mainstream content on the PC are still single and dual-thread at best with a few outliers go beyond that.

Homework for Krogoth: research game performance on systems with just two threads vs. six+ threads.

Topinio · Fri Oct 13, 2017 1:26 am

Airmantharp wrote:
Krogoth wrote:
The majority of the games and mainstream content on the PC are still single and dual-thread at best with a few outliers go beyond that.

Homework for Krogoth: research game performance on systems with just two threads vs. six+ threads.

Pssst, Krogoth, mate. Over here, check it out, don't grass me up to Mr. Airmantharp though mate, yeah, don't wanna 'nother detention again :wink:

.

synthtel2 · Fri Oct 13, 2017 2:19 am

Krogoth wrote:
I did read the review and it doesn't change the notion at all.

How do you intend to explain the 8700K's commanding lead over the 7700K, then? No, background load isn't it. If background load is taking more than a quarter of a single core, your system has issues.

Krogoth wrote:
Gaming consoles =! PCs

They kinda do equal PCs though. Are you really gonna put the work in to multithread on consoles and then just throw it out the window for PC? No, no you're not. Even if you wanted to, you'd just have to do a whole lot of work distribution architecture all over again for PC. Aside from that, if you didn't, your 30 fps CPU-heavy console games would need a 5.0+ GHz SKL/KBL/CFL just to maintain 60 fps, because two of Intel's best just aren't that much faster than six 1.6 GHz Jaguars.

Krogoth wrote:
frankly coding multi-threaded software that isn't hilariously parallel is hard and time consuming.

Yeah, but not half as much as you think, and we've got some very smart people working on it (and sharing their ideas - we're not exactly a secretive industry). Believe it or not, game developers are actually capable of solving difficult problems.

Krogoth wrote:
The killer app for multi-core CPUs for gaming needs isn't gaming itself.

Do you have any idea how much better games could be if we suddenly had 2-4x the CPU power we currently do? I'm looking forward with glee to the core count wars AMD hopefully just triggered, and not just for compiling. :wink:

Krogoth · Fri Oct 13, 2017 6:00 am

synthtel2 wrote:
How do you intend to explain the 8700K's commanding lead over the 7700K, then? No, background load isn't it. If background load is taking more than a quarter of a single core, your system has issues.

You may want to double-check the data from a variety of sources again. Outside of a few mainstream tier outliers, the 7700K and 8700K are neck to neck under majority of mainstream tier apps and games as expected because they have the same turbo speed for anything less than 4 threads. The 8700K only shows a noticeable gain if you do content creation, CPU streaming under some games, or throw professional-tier applications that do take advantage of the extra threads. It is not a 50% gain either because the turbo speed with 6 cores is capped at 4.3Ghz unless you use "Mutli-core Enhancement" which is basically arm-chair overclocking a.k.a forcing the CPU to run at max speed with all cores enabled.

The adoption and effectiveness multi-threaded software has little do with talent of the developers in question. It has far more to do with the economics. It costs extra man-hours to properly code and debug software that multi-threaded. Not everything is hilariously parallel and there is diminishing returns. The potential benefits may not justify the extra expenditure for it. This is precisely why the bulk of mainstream software (games included) is single-threaded and dual-threaded at most. This reality isn't going to change either.

Intel never bother going beyond 4-cores for their normal desktop tiers until Ryzen 5 and 7 started to put pressure on them, because there's no mainstream demand for it. The recent uptake gaming streaming show that there is a non-prosumer-tier demographic that does use more then 4-cores for their needs. This is where Ryzen 5 and 7 managed to outshine their Kaby Lake counterparts. Intel just hastily responded by throwing two extra cores on the die. Coffee Lake is nothing more than damage control for Intel's mainstream tier.

Krogoth · Fri Oct 13, 2017 6:14 am

Airmantharp wrote:
Krogoth wrote:
The majority of the games and mainstream content on the PC are still single and dual-thread at best with a few outliers go beyond that.

Homework for Krogoth: research game performance on systems with just two threads vs. six+ threads.

Already did it and still came to the same conclusion. Outside of a small minority of mainstream applications and games, the benefits of going from dual-core to quad-core are still kinda small. The majority of the reviewers out there are cherry-picking games that are known to use more than two-threads (Doom (2016), Witcher 3, GTA 5, Battlefield 4/1). It is no shock that you see considerable returns, however they are the exceptions not the rule as far mainstream applications are concerned. The benefits of going beyond quad-core are even smaller with the aforementioned games unless you do CPU streaming at the same time.

I find it bloody hilariously that the same gaming crowd that harp on Ryzen's "poor gaming performance" and brushing off its content creation and general compute prowness while claiming that 7600K/7700K is all you need now suddenly treats the entire 6-core Coffee Lake line-up like it is best thing since sliced bread.

Glorious · Fri Oct 13, 2017 7:23 am

Krogoth wrote:
The majority of the reviewers out there are cherry-picking games that are known to use more than two-threads (Doom (2016), Witcher 3, GTA 5, Battlefield 4/1)

Oh, those games? The best-selling, very popular ones?

Krogoth wrote:
It is no shock that you see considerable returns, however they are the exceptions not the rule as far mainstream applications are concerned.

He said gaming performance, which means he's talking about games for which performance matters. Thus, no, we're not talking about minecraft, and no, we're not talking about "mainstream applications".

Krogoth wrote:
The benefits of going beyond quad-core are even smaller with the aforementioned games unless you do CPU streaming at the same time.

I have a 4C4T CPU playing Battlefield 1. I would absolutely recognize the benefit of having more than 4 cores. It could potentially double my minimum frame rate.

But, yeah, I just cherry-picked that one along with the 2-3 million other people who bought it for the PC (and 15+ million who bought it overall).

I find it bloody hilariously that the same gaming crowd that harp on Ryzen's "poor gaming performance" and brushing off its content creation and general compute prowness while claiming that 7600K/7700K is all you need now suddenly treats the entire 6-core Coffee Lake line-up like it is best thing since sliced bread.

I find it sad that you're laughing at something airmantharp didn't say.

He said two threads to 6+ threads.

Work on your reading "prowness."

synthtel2 · Fri Oct 13, 2017 6:00 pm

Krogoth wrote:
You may want to double-check the data from a variety of sources again. Outside of a few mainstream tier outliers, the 7700K and 8700K are neck to neck under majority of mainstream tier apps and games as expected because they have the same turbo speed for anything less than 4 threads. The 8700K only shows a noticeable gain if you do content creation, CPU streaming under some games, or throw professional-tier applications that do take advantage of the extra threads.

I did double-check the data before posting that, and it said this:

What's neck-and-neck about this again? Alright, as you say, it's a bit of a small sample size. Other sites are also showing quite real and widespread gains though, and said gains simply wouldn't exist if two threads were the standard.

Krogoth wrote:
The adoption and effectiveness multi-threaded software has little do with talent of the developers in question. It has far more to do with the economics. It costs extra man-hours to properly code and debug software that multi-threaded. Not everything is hilariously parallel and there is diminishing returns. The potential benefits may not justify the extra expenditure for it.

Yes, cost-benefit analysis is involved. You've obviously never done it. We're nowhere near Amdahl's law and the available gains are a lot bigger than you think, *and* multithreading usually isn't even time-consuming compared to other stuff in game dev.

Krogoth wrote:
Already did it and still came to the same conclusion. Outside of a small minority of mainstream applications and games, the benefits of going from dual-core to quad-core are still kinda small.

Care to disable half your 3570K and then try a few games? Spoilers: it's ugly.

Topinio · Sat Oct 14, 2017 3:15 am

Krogoth wrote:
Already did it and still came to the same conclusion. Outside of a small minority of mainstream applications and games, the benefits of going from dual-core to quad-core are still kinda small. The majority of the reviewers out there are cherry-picking games that are known to use more than two-threads (Doom (2016), Witcher 3, GTA 5, Battlefield 4/1). It is no shock that you see considerable returns, however they are the exceptions not the rule as far mainstream applications are concerned. The benefits of going beyond quad-core are even smaller with the aforementioned games unless you do CPU streaming at the same time.

From 2010, from arguably the most mainstream game of the decade.

Krogoth · Sat Oct 14, 2017 8:10 am

Topinio wrote:
Krogoth wrote:
Already did it and still came to the same conclusion. Outside of a small minority of mainstream applications and games, the benefits of going from dual-core to quad-core are still kinda small. The majority of the reviewers out there are cherry-picking games that are known to use more than two-threads (Doom (2016), Witcher 3, GTA 5, Battlefield 4/1). It is no shock that you see considerable returns, however they are the exceptions not the rule as far mainstream applications are concerned. The benefits of going beyond quad-core are even smaller with the aforementioned games unless you do CPU streaming at the same time.

From 2010, from arguably the most mainstream game of the decade.

WoW is still dual-threaded like the majority of gaming titles out there in the field. The only reason you see a small jump from gaining an extra gain is because of OS and other overhead in an "artificial" dual-core setup. Just notice how there's no returns after going beyond three threads and the 6-core Phenom is only faster when it is unlocked because it has full access to L2/L3 cache pool at its disposal. "Artificially" gimping silicon's core-count can possibly restrict is access to its cache pool depending on CPU topology.

The reason why reviewers pick the outliers is because they want stuff that stresses the CPU. The reviews would be awfully boring if they stuck what the masses are playing these days (LOL, TF2, COD, CS:GO, DOTA, MMORPG stuff) not stuff that taxes current CPUs. The listed 99th percentile FPS ratio graph only includes the titles that do take advantage of more then two threads. If you were to throw in content that is still stuck in two-threaded world (What the masses still play to this day). All of the quad-core CPUs and beyond would be around a much tighter cluster distancing themselves away from dual-core chips by a small gap. The differences between the quad-core chips and beyond would be just price.

Redocbew · Sat Oct 14, 2017 11:20 am

I wonder if there's anyone out there who hates branch prediction or out of order execution the way you hate SMT. Of course that'd be ridiculous. Branch prediction and out of order execution are ubiquitous and have been a common feature of modern desktop CPUs for years now. Things just wouldn't be the same without them.

Oh, wait...

Seriously though dude, this is just getting silly. You keep saying the same thing over and over again with no sources or backing behind it. I'm not a big fan of Windows these days, but it clearly doesn't suck as much as you think it does. If what you're saying was true and there really was so much overhead just for the OS it's self, then there would be no argument about it. Performance would suck across the board, for everything, and it's just not that way.

Sat Oct 14, 2017 11:41 am

A bit late to this thread... but anyhow:

Early SMT implementations were indeed a little dodgy, and this was compounded by the fact that OS CPU scheduling algorithms didn't deal with it properly either. The situation is substantially better now, but there are still corner cases where it doesn't work well, and it can also result in confusion (e.g. it can appear that your system is only ~50% loaded, when it's effectively a lot higher since those "idle" cores are actually virtual SMT cores).

But for many workloads, SMT improves performance without a significant increase in die size of power consumption. Implementing 2x the number of "real" cores would make the CPU a lot more expensive and result in significantly higher power consumption and reduced efficiency.

That said, it's a little unfair to compare SMT to out-of-order execution or branch prediction, since the former has potential upside and downside (tilted to the upside these days now that it is a mature tech), whereas the absence of the latter would likely result in worse performance across the board.

Redocbew · Sat Oct 14, 2017 12:13 pm

Yeah I suppose that's true. There are good reasons to dislike SMT, but in general it seems like a good thing to me. The effects of SMT(namely having virtual cores which otherwise wouldn't be there) are much more easily visible than that of branch prediction or many other features which I guess is part of the problem. If it just sorted of faded away into the background, then it probably wouldn't have received so much attention. The segmentation games of using SMT to help define the differences between an i3, i5 and i7 probably haven't helped with that either, but those are only quasi-technical things. As a developer this is all stuff way outside my specific field, so I imagine I might be a bit more measured in my opinion if I had to deal with the corner cases where SMT is problematic. Overall it seems like most people designing chips these days have decided that the pros of SMT outweigh the cons, and since I'm not one of them I'll just have to take their word for it.

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