Quad Core vs Dual Core

[artmaltman]

Do any of you know whether quad core is an advantage over dual core when it comes to editing photographs in Lightroom and Photoshop?

I'm debating MacBook pro 13" (dual) vs 15" (quad) and really, I'd rather have the smaller one. The issue is whether the quad core would make Photoshop and Lightroom run noticeably faster when editing photographs. I get into very detailed editing on headshot. Lightroom in particular will bog down tremendously sometimes.

All of my software is most current version, always. Currently using a 2015 MBPr 13" maxed out I7 16gig memory. Considering the latest (2017) MBPr models.

My impression is that Photoshop and Lightroom use only one core, so what matters more is the speed of that one core, in which case the 13" at 3.5mhz is actually faster.

SO, do any of you know whether quad core is an advantage over dual core when it comes to editing photographs in Lightroom and Photoshop?

Thanks!

Art

ps: I have read that use of the dedicated GPU on a 15" would actually slow down these programs when editing photographs. That it's best to turn off the dedicated GPU. Have any of you confirmed that via testing?

 

[Linwood Ferguson]

Top tip! I can see four graphs, so I must have four cores. But "About this Mac" says I have one processor and a total of two cores...

As Hal mentions that likely means Hyper Threading is on. This is controlled in your bios, not in windows. The normal default is on, as it makes systems "look" more substantial than otherwise.

In days past it was questionable whether HyperThreading was a good thing, but with LR 7.1 and soon to be released 7.2, HyperThreading is a good thing, as Adobe counts cores and does not turn on certain optimizations unless you have enough. Four is sadly probably not enough for much of the performance benefit that they are working on. Four is better than two (so on is better than off), but four is not where you see the real benefit from the new lightroom performance changes.

 

[PhilBurton]

As Hal mentions that likely means Hyper Threading is on. This is controlled in your bios, not in windows. The normal default is on, as it makes systems "look" more substantial than otherwise.

In days past it was questionable whether HyperThreading was a good thing, but with LR 7.1 and soon to be released 7.2, HyperThreading is a good thing, as Adobe counts cores and does not turn on certain optimizations unless you have enough. Four is sadly probably not enough for much of the performance benefit that they are working on. Four is better than two (so on is better than off), but four is not where you see the real benefit from the new lightroom performance changes.

Ferguson,

How many cores are enough for LR 7.2?

Phil

 

[Linwood Ferguson]

Ferguson,

How many cores are enough for LR 7.2?

Phil

I am not aware that 7.2 changed the rules, I think 7.0 or 7.1 is when they put in the checks. 7.2 is vastly better at some things, however, so you benefit more there.

I found 8 (4 x hyperthread) worked, and 4 (turn HT off) did not, so somewhere between 4 and 8. I did not have a way to try 6 (which some may have with non-HT architectures).

Basically, as best I can tell, LR throws in a lot more parallelism in later versions, and it is more effective in each version, but they do not turn it on if they think you have too few cores to have your computer still perform adequately while they do a lot of parallel work.

One quick way to tell if you have enough cores (at least to start this) is do a largish import, and if it starts building previews while it is still copying files, it has enough cores. I do not know if there are lots of additional things that start at 8, 12, 16, etc. cores, but that seems to be a good, quick test of the basic minimum level.

 

[Linwood Ferguson]

Incidentally, the above mentioned test to see if you have enough cores to shave the parallelism performance stuff really kick in is in 7.1 (maybe in 7.0 I can't recall). Here's what it looks like just doing an import if it's building in parallel, it shows two things, and the bottom line runs, completes (it does the first few) then runs again and finishes that set, and continually runs until all previews are built -- which may be pretty close to when the import finishes if you have a slow card reader.

 

[Zenon]

As Hal mentions that likely means Hyper Threading is on. This is controlled in your bios, not in windows. The normal default is on, as it makes systems "look" more substantial than otherwise.

In days past it was questionable whether HyperThreading was a good thing, but with LR 7.1 and soon to be released 7.2, HyperThreading is a good thing, as Adobe counts cores and does not turn on certain optimizations unless you have enough. Four is sadly probably not enough for much of the performance benefit that they are working on. Four is better than two (so on is better than off), but four is not where you see the real benefit from the new lightroom performance changes.

What do you mean by - on is better than off?

 

[Linwood Ferguson]

What do you mean by - on is better than off?

On systems where bios and processor support it, hyperthreading can be turned on or off. In LR7 and above I suggest turning it on is better. On is usually the default, so this generally means doing nothing.

In LR5, and I think most if not all of LR6, my testing showed Hyperthreading turned off to be slightly better. That is normally the case when an application has limited parallelism, i.e. if it is doing only 1, 2, or 3 things at a time (for example), then a 4 core system running as 4 will run faster (off) than a 4 core system pretending to be 8 (which is what HyperThreading really is -- a hardware/software cooperation to pretend to be more cores than there are). This presumes the application does the same thing regardless of number of cores, and one is measure which is better.

In LR7 something different happens -- LR decides what to do based on the number of cores, so it is not a question of whether 4 or pseudo-8 is better, but rather that as a side effect of turning on hyper-threading (if you have 4 real cores) you are also turning on lots of other performance enhancements. So definitely "On" is better now for 4 core systems for sure.

Now is on better for 8 core systems (that support it)? I do not know, as then I think Adobe would have performance enhancements turned on at 8, and also for pseudo-16, and we would be back to measuring apples vs apples . I do not have a 6 or 8 core system to test (and as mentioned I never tested 6 so do not know where the break point is).

By the way... I do not want to leave the impression that turning enhancements on or off is some elitist role, and they are penalizing small core systems needlessly -- the rationale appears to believe that if turned on for small core systems, it would consume the system enough it would otherwise hang, and you could not easily access it (e.g. to stop preview build or some such). Did they get the breakpoint right?

 

[David Gordon]

On systems where bios and processor support it, hyperthreading can be turned on or off.

Must be a PC thing, I don't think Mac users have the option. (Unless there's some kind of terminal command, but I’ve never heard of this.)

 

[Hal P Anderson]

I don't think Mac users have the option.

It isn't an operating system command. It happens at a lower level than that. Linwood mentioned earlier that it's a BIOS command. On Windows (and probably on a Mac) you can hold down a special key while booting the system that brings up a screen that lets you modify how the hardware works. One of the things you can do there is to turn hyperthreading on and off.

 

[Johan Elzenga]

It isn't an operating system command. It happens at a lower level than that. Linwood mentioned earlier that it's a BIOS command. On Windows (and probably on a Mac) you can hold down a special key while booting the system that brings up a screen that lets you modify how the hardware works. One of the things you can do there is to turn hyperthreading on and off.

Macs don't have a BIOS. Macs boot using EFI. There is no equivalent to the BIOS settings on a PC. There are some things you can do at startup (Mac startup key combinations), but nothing like turning on/off hyperthreading.

 

[Zenon]

Thanks everyone.

 

[Linwood Ferguson]

Macs don't have a BIOS. Macs boot using EFI. There is no equivalent to the BIOS settings on a PC. There are some things you can do at startup (Mac startup key combinations), but nothing like turning on/off hyperthreading.

On PC's with EFI you can set it there also. I used the term "Bios" really to imply "whatever is in your hardware that starts it up".

Some Mac's with intel chips do support it, and apparently (google is my friend) you can disable it, as described in this posting on stackexchange. note I'm not suggesting you should disable it. the posting is a bit old but I saw other references to the same program from mid-2017.

How to disable HyperThreading on Mac OS X Yosemite?

Note I can barely spell Mac so I know nothing at all about the program mentioned and whether this works, only that HyperThreading is innate in certain Intel CPU's, and Mac uses some of them, so yes, you have it.

 

[Hal P Anderson]

Thanks, Johan. An Intel-based computer without a BIOS. Who would have thought?

 

[Zenon]

Now I'm not so hyper about figuring it out.

 

[Linwood Ferguson]

Thanks, Johan. An Intel-based computer without a BIOS. Who would have thought?

I haven't had a (non-UEFI) bios in any computer for years, and I'm pure Windows/Intel.

Heck, even my VM guests running in HyperV use UEFI.

Time passes when you're out shooting.

 

[Johan Elzenga]

On PC's with EFI you can set it there also. I used the term "Bios" really to imply "whatever is in your hardware that starts it up".

Some Mac's with intel chips do support it, and apparently (google is my friend) you can disable it, as described in this posting on stackexchange. note I'm not suggesting you should disable it. the posting is a bit old but I saw other references to the same program from mid-2017.

How to disable HyperThreading on Mac OS X Yosemite?

Note I can barely spell Mac so I know nothing at all about the program mentioned and whether this works, only that HyperThreading is innate in certain Intel CPU's, and Mac uses some of them, so yes, you have it.

Not really. Did you read the last sentence in link? "However, after restarting your Mac it will be enabled again.". And MacOS X Yosemite is very old. XCode has changed a lot since then. It no longer contains all kinds of separate applications, it's one single package right now. So I doubt that the method in that link is still valid.

 

[Linwood Ferguson]

So then in current Mac OS there's no way to permanently disable hyper-threading?

I guess that's in keeping with Apple's "have it our way" philosophy in most things.

 

[tspear]

Thanks, Johan. An Intel-based computer without a BIOS. Who would have thought?

Actually, EFI is BIOS. Well BIOS on steroids. It abstracts a slightly higher level above the core BIOS hardware layer. In theory this will improve performance, and reduce driver and other issues commonly found in the OS. The idea is to provide a more common abstraction layer.

Tim

 

[PhilBurton]

Macs don't have a BIOS. Macs boot using EFI. There is no equivalent to the BIOS settings on a PC. There are some things you can do at startup (Mac startup key combinations), but nothing like turning on/off hyperthreading.

No PC, not based on a modern motherboard, would use the old classic BIOS. All modern designs utilize UEFI interface to control hardware. However, the term "BIOS" lingers on. The BIOS was invented, or at least popularized by IBM when the brought out their PC in 1981.

Phil

 

[Johan Elzenga]

Whatever. You guys are missing the point. The point is that -at least AFAIK- you can't disable hyperthreading on a Mac running the latest MacOS X version.

 

[Linwood Ferguson]

Whatever. You guys are missing the point. The point is that -at least AFAIK- you can't disable hyperthreading on a Mac running the latest MacOS X version.

Yeah, I've been curious since this started, and there is tellingly little on the subject. I've found a couple places where they say you can use "instruments" to disable it (whatever that is) but that it doesn't persist.

Michael Tsai - Blog - Bug in Skylake and Kaby Lake Hyper-threadingMichael Tsai - Blog - Bug in Skylake and Kaby Lake Hyper-threading

I'm not sure if that works or not, but it has a recent date. It concerns a bug related to HyperThreading in specific CPU's. But there's very little discussion about HyperThreading in Mac's, I guess, because Apple turns it on and makes it stay on for either all, or all but a persistent few who dig deeply.

Which again... for later versions of Lightroom, is probably the best bet. And on old versions the downside was very, very minor of being on.

 

[Johan Elzenga]

Apparently 'Instruments' was one of the many apps that used to be part of XCode (Apple's programming environment). In the past, XCode was a folder that contained lots of individual apps, and templates and other stuff. The latest version of XCode isn't like that anymore. It's a single, huge application (11 GB) now. Because Mac applications are 'packages' (folders that behave like they are files), the 'Instruments' app may still be in the package somewhere, but you sure won't find it using Spotlight.

UPDATE: I peeked inside the XCode package and 'Instruments' is indeed still in there. So people who know how to do this may still use 'Instruments', but apparently that will only turn off hyperthreading until a restart.