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So everyone is getting the 6-core, why?

A

ApplesAOranges

macrumors 6502
Original poster
Jan 7, 2011
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Based on what I´ve followed on this forum and other forums, everyone is getting the 6-core, why is that? What´s wrong with the 8-core or 12-core?

Some even say the 6-core is faster than the 12-core. How can this be? 12-core is $3000 more.

Will I waste my money if I get the 12-core?
 
The more cores, the more each individual's clock speed goes down. It's kind of confusing and counterintuitive. So, when doing tasks that don't require multiple cores – say, Photoshop – you're only taxing a single core, so it's the single core speed that counts. For multiprocessor tasks – for instance, 3D rendering – more cores will be accessed.

So it's a trade off. The SINGLE core speed for the 8 Core and 12 Core is actually slower than the 6 and 4 core. But of course, once you hit that render button in a 3D program, you'll see speed increases you wouldn't in less cores.

It's explained here:

http://macperformanceguide.com/MacPro2013-CPU-GPU-choice.html

And here:

http://www.marco.org/2013/11/26/new-mac-pro-cpus

So, you have to find that sweet spot based the type of work you do and what you can afford. For a lot of people, 6 cores seems to be that spot – faster clock speed for single core than the 4 core; but more cores for multiprocessor tasks. Hopefully that makes sense.
 
12 cores or even 8 cores are very specific use cases as most programs don't make much use out of them. The 4, 6 and 8 all have top single core turbo boost speeds of 3.9GHZ the 12 core is lower. See this table. The 6-core is the sweet spot for performance per dollar. The 12 core is very expensive and the 8 core is fairly expensive.

As the chart shows the 8-core only bests the 6-core when 2 cores are active at full boost and only by 0.1GHz and then only if you need the 2 extra cores. Otherwise the 6 is equal or better at all other core usage. You can also see the 4-core is identical to the 6-core and the only benefit is the 2 extra cores.
 

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A note on that graphic – the red rows are not options for the nMP, they're imaginary. But the chart does give you a good idea of how the speeds go down as the core go up.
 
What everybody says here. The TDP is the same for all the chips, 130W I believe. So Intel has to balance performance with Turbo Boost. More cores = lower base clock, and they all have different Turbo steps. The hex core is the sweet spot for most people, especially considering costs. To go to octo is another $1500 or whatever, but you drop a huge 700MHz, and only gain two more cores. Going from quad to hex gives you the same steps with a minor drop in base clock, for 50% more cores. Win!
 
Cubemmal said:
What everybody says here. The TDP is the same for all the chips, 130W I believe. So Intel has to balance performance with Turbo Boost. More cores = lower base clock, and they all have different Turbo steps. The hex core is the sweet spot for most people, especially considering costs. To go to octo is another $1500 or whatever, but you drop a huge 700MHz, and only gain two more cores. Going from quad to hex gives you the same steps with a minor drop in base clock, for 50% more cores. Win!
Click to expand...

although with 8 core you get just over 3mb cache per core as opposed to 2mb per core on the 6 core

i don't really know what L3 cache does to know if this is significant or not
 
jondunford said:
although with 8 core you get just over 3mb cache per core as opposed to 2mb per core on the 6 core

i don't really know what L3 cache does to know if this is significant or not
Click to expand...

Cache is based on workload and not per core. The data set it holds is shared amongst the cores.
 
There's no exact answer, it depends on your workload which is always changing anyhow. Regardless hex appears to be what Intel targeted as the sweet spot, with quad holding down the low end. In two years it will be Octo as the sweet spot no doubt, as smaller transistors allows for more cores with the same TDP.
 
ApplesAOranges said:
Based on what I´ve followed on this forum and other forums, everyone is getting the 6-core, why is that?
Click to expand...
That's all mommy and daddy will pay for.

And the 12-core unit would heat up the basement too much anyhow.

:D

There are probably 8-core and 12-core buyers here, they simply just keep their mouths shut and get on with business. Discretion is not a common trait in these tech gadget forums, I know.

This bboard gets more shrill with every passing year. Highly entertaining, if decidedly less useful. Oh well, that's the way most Internet sites evolve...
 
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The 6-core really probably is the 'sweet spot' in this lineup. I picked up a 12-core because we have very specific workloads that will substantially benefit from it (multi-day video encoding jobs), but if we deploy other Mac Pros as day-to-day workstations around here (we're a post facility), they'll likely be 6-core machines, and if I could justify the price tag of a Mac Pro for personal use that would absolutely be a 6-core machine as well.
 
As i understand, the 8 and 12 core versions of old Mac Pro had two separate processors. (correct me if i'm wrong)
Is this the same with the nMP?
Is the 12 core model a single 12-core processor or 2 6-core processors?
 
arbitrage said:
12 cores or even 8 cores are very specific use cases as most programs don't make much use out of them. The 4, 6 and 8 all have top single core turbo boost speeds of 3.9GHZ the 12 core is lower. See this table. The 6-core is the sweet spot for performance per dollar. The 12 core is very expensive and the 8 core is fairly expensive.

As the chart shows the 8-core only bests the 6-core when 2 cores are active at full boost and only by 0.1GHz and then only if you need the 2 extra cores. Otherwise the 6 is equal or better at all other core usage. You can also see the 4-core is identical to the 6-core and the only benefit is the 2 extra cores.
Click to expand...

That's a useful chart, So for example if I bought a 12 core (which I am close to doing) and I booted it up in bootcamp to game which I assume is a single threaded task? it would Turbo boost to 3.5GHZ (or 3.9GHZ on an 8 core). But if I was using After effects in OSX using all the cores the speed would only ever be 3GHZ? Sorry just getting my head around this boost business. ;)
 
For me the "Why"? came down to a simple factor: cost. I had a set amount of cash on hand to spend on this machine, so then the task became one of choosing the combination of options that got me the most "bang for my buck" while not breaking that limit. The 6 core option seemed to me to be the best fit to free up spending on other items.
 
ApplesAOranges said:
Based on what I´ve followed on this forum and other forums, everyone is getting the 6-core, why is that? What´s wrong with the 8-core or 12-core?

Some even say the 6-core is faster than the 12-core. How can this be? 12-core is $3000 more.

Will I waste my money if I get the 12-core?
Click to expand...

Depends what you need it for.

If I were buying I'd by the 12 core but only because that would give me 24 render buckets in Modo vs the 12 I currently have which would effectively halve my render times.

The choice really depends on what kind of apps you are running.
 
Same thing others have said, the 6-core combined with the D500 cards really is the sweet spot of performance and having some longevity.
 
I was actually expecting the 4-core and 8-core to be much more popular over the 6-core, based on available CPU benchmarks. The 12-core is certainly very much a niche product for very specific uses. The 4-core is ideal for single-threaded operations, of course. Between the 6-core and 8-core, though, I would have figured the advantages of the larger L3 cache and additional cores would have been well worth the additional cost.

Now, that said, I'm hoping we get real-world performance data soon, particularly with the GPUs. I wouldn't buy any Mac Pro until we have hard data.
 
On a more serious note, depending on your workflow, it might make more sense to stick with a basic 6-core Mac Pro and pick up a couple of quad-core Mac minis.

If you have tasks that are largely CPU-bound, it would make more sense to offload that work to the Mac minis, leaving the Mac Pro free to do other work. Pegging all the CPUs on your local machine will make it sluggish.

If you work in a workgroup, the Mac mini render farm makes even more sense, as multiple users can access those resources.

Unsurprisingly the four-core configuration is not particularly popular: there are already quad-core Mac minis and iMacs (albeit the CPUs are less powerful in those cases).
 
mrxak said:
I was actually expecting the 4-core and 8-core to be much more popular over the 6-core, based on available CPU benchmarks. The 12-core is certainly very much a niche product for very specific uses. The 4-core is ideal for single-threaded operations, of course. Between the 6-core and 8-core, though, I would have figured the advantages of the larger L3 cache and additional cores would have been well worth the additional cost.
Click to expand...

The 4-core CPU is only 200MHz faster than the 6-core CPU.

For 4-core, there's the iMac.
 
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