Turbo Boost for Single Threaded Tasks

[bslarch]

Hi all,

Just a quick question regarding single threaded tasks.

The company I work for exclusively uses macs and will be getting me one of the new iMac pros. For the applications I use, a lot of the tasks are single threaded, and then later use all cores for rendering.

What I’m wondering is, does turbo boost kick in for single threaded tasks? I ask because the base 8 core Intel Xeon W version of the iMac Pro has a 3.2GHz base frequency and 4.2GHz turbo boost, while the 10 core version has a base of 3.0GHz and a boost of 4.5GHz.

Therefore if single threaded tasks will be turbo boosted, then the 10 core option seems to make more sense. However I always that that the fewer the cores, the higher the frequency, the better the single threaded performance. So I guess I’m a little confused.

Any help will be greatly appreciated! Thanks

 

[bigpinkdragon286]

The turbo boost may indeed be higher on the 10-core part, but do you really think you're going to be seeing the difference between your CPU boosting to 4.5 GHz vs 4.2 GHz? Probably not as much as you might suspect, especially if the human is the bottleneck.

However, I suspect you will see a tangible difference in your 8-cores rendering at 3.2 GHz rather than having 10-cores at 3.0 GHz. If you're saturating your CPU with a lot of rendering, you're going to get more work out of the 10-core system, even if it's slightly slower when spooled up fully. Despite the slower speed cores, the 10-core still has in the neighborhood of 15% more rendering power, all other things being equal.

I'm only using back of the napkin calculations here, but that can really add up if you have a lot of rendering to get done. We're talking about saving 8+ minutes out of every hour of rendering between the two CPUs.

Whether this is something your company wants to pay what I can only imagine is a premium for, is between you and them, but I do feel there is a case which can be made that there is the potential for higher productivity with the 10-core system.

 

[bslarch]

Thanks for the detailed response!
I think I am more interested in better single threaded performance for the 3D applications I use, rather than better render times in the end. For this, the 10 core option seems the better choice, even if the difference is so small as you point out. But anyways, it seems for both cases, the 10 core is the better option right (single thread and rendering)?

So I was correct in my assumption right, that turbo boost kicks in for single threaded calculations?

I’m just noticing with my computer at home that I’m really loosing a lot of time (a few seconds every task, which REALLY adds up when you need to work quickly). So I want to make sure that at work, I’ll at least have a much more efficient experience.

 

[bigpinkdragon286]

Yes, I think if the numbers you posted are the correct ones, no matter how you slice it, that 10-core is a better performer than the 8-core.

If the human is the bottleneck, such as with typical office PC tasks, you won't notice the extra single threaded performance, but there are certainly cases where you can see the difference. Just, the typical user doesn't tend to fall into that category. If you're the one that does, by all means, make your case to your company, especially if you work with this machine 5 days a week.

The basics behind turbo is, the CPU has a maximum power envelope it's allowed to work within, and as long as it can maintain it's integrity and compute values accurately, and fulfill the specs it needs to meet, why not clock it accordingly when lightly loaded! CPUs generally clock lower the higher the number of active cores due to power delivery and heat dissipation requirements. Clocking a single or even a few lightly loaded cores well beyond what you would normally see all of the cores run at, is usually perfectly fine. The CPU will manage the turbo such that the CPU is always operating as it should for, as soon as the CPU doesn't operate correctly, you'll be getting the equivalent of a Windows BSOD. No idea what the Mac equivalent is, but you get the gist. The lighter your loading on the CPU, the more favorably it can clock itself, whether that's down to idle speeds to save power, or to maximum boost to chew through lightly threaded work at an accelerated rate.