What will Logic Studio utilize- 4 core Mac Pro, 8 core Mac Pro, i7w/HT iMac

Logic 9 will NOT use logical cores, so hyperthreading is not a technology of any use in Logic.

I'll go for an 8 cores, as for me, Logic is fine utilizing all the 8 cores on my 2008 MacPro.

As for the RAM, that's the bad point in Logic 9. Logic, as a 32bits app, can address only 4Gb of RAM (reality is closer to 3.6). And Logic 9 uses way more RAM than Logic 8 (600Mb more), so until Apple dare to make Logic a 64 bits app, you'll have to deal with it.

As far as I can tell from testing it out, it looks like logic currently will use 8 cores, whether they are 8 full cores or four full cores plus four HT cores.

So on a 4 core machine with HT such as the quad MP or the new iMac, logic sees 8 cores and can use them all. On an 8 core machine with HT, it will use the 8 main cores but not the HT which sit there unused - this looks like a limitation of Logic and not of HT since they are used on a 4 core machine. Hopefully there will be a future update of Logic that can use 16 cores (or even better, looks at the number of cores on the machine and uses that many).

This is from testing on an 8 core machine and either disabling HT or disabling four of the eight cores and leaving on HT. Someone with a quad HT mac (either the imac or MP) can test this and confirm - does it show up as eight cores in Logic (and Activity Monitor) and are all used. I should have access to an i7 soon, so I'll try it out.

Disabling HT with 8 cores makes little difference. Disabling four of the 8 cores makes a very small difference - instead of using the 8 main cores, it uses four plus the four HT cores, giving performance almost as good as eight full cores. Disabling HT when only four cores are active cuts performance by about half, so it definitely looks like HT is used in a quad configuration.

G-BoX 988, where did you hear that Logic can't use HT cores? Or have you tested it out and seen different results? I can see why it would look like Logic couldn't since it doesn't use them on an 8 core machine, but it seems like the limiting factor is Logic itself (8 threads?) and not the HT. Unfortunately, I haven't found any official documentation either way.

As for ram, the theoretical limit is 4 gigs for any 32 bit app which includes virtual memory, but in real world use it is less, often 2.7 gigs or less. And it can vary based on plugins used and other things, but in many cases, L9 can leave less usable memory than L8. EXS is able to stretch the memory limit, so if that is your main sampler you might be able to use more than the 4 gigs. I'd probably go with 4-6 gigs to run Logic unless you know you are running plugins (or other standalone audio apps) that can use the extra memory.

Just tried running Logic on an i7 quad, and logic shows eight CPU meters, and Activitiy Monitor shows activity on all eight cores. Unfortunately, it looks like the tool I use to disable HT and cores isn't compatible with i7, so I can't try that to see if track/plugin count goes way down, but from what I'm seeing and what I saw on the other machine I'd guess that is likely.

As for raw performance, the i7 is pretty darn impressive with Logic, the particular machine I'm testing now can actually run more plugs than the latest base 8 core machine I tested.

I answered that above - on the 8 core mac pros with HT, it uses eight cores, generally the eight main cores and not the HT cores. This looks like more like an 8 thread limitation than a HT limitation since i7 machines show up as 8 cores in Logic and the HT cores are used.

Correct. It is no HT issues with Logic but the 8 core limit, virtual or real doesn´t matter.
Strange enough Logic 8 showed 16 cpu meters but with no activity on the last 8 ( 9 in fact ).

DrumStudio wrote:
Please read info from above users. One states logic only shows 8 cores on a 16 virtual core machine, next has 8 core i7 showing 16 cores 8 not in use.

The only post I see that says Logic doesn't use HT cores is from a guy who doesn't have a machine that uses HT, so I have to assume he was just making a guess or read something somewhere but hasn't tested it out. I asked him to clarify, but no response.

I don't see any posts saying that Logic 9 showed 16 cores on any machine (I haven't tested it with L8), which one are you talking about?

So... can logic use 16 cores?

Not yet, Logic only uses 8 cores, I have never seen anyone who has claimed otherwise.

Why would it display this on an i7 but not 2xquad core mac pro w/hyperthreading?

It doesn't show 16 on any machine - Logic shows 8 on i7 quad and 8 on eight core xeon, presumably because Logic is limited to eight cores, whether they are full cores or HT cores.

Can anyone else confirm or supply a link in the manual or official apple/logic statement?

Firechild just confirmed it, but others are welcome to confirm as well since you don't seem to believe it. Logic doesn't mention it in the manual or anywhere else, I don't believe they have ever made public statements about how many cores Logic (or any other Apple app) uses, except I believe for the release notes when using all four cores on quad G5s were first supported. It would be great if apple published that info, but I wouldn't get your hopes up (and asking on here isn't going to get apple to post it). I suppose you could call Logic tech support, but I suspect they have no idea.

To sum up:

8 core xeon mac pro:
8 main cores
8 HT cores
16 show up in Activity Monitor
8 show up in Logic

4 core i7 iMac:
4 main cores
4 HT cores
8 show up in Activity Monitor
8 show up in Logic

If anyone with either of these machines wants to test out and confirm this, it would be appreciated.

With hyperthreading the math unit (FPU) in one core is shared between two hyperthreads. But because Logic's DSP code is heavily based on math, hyperthreading doesn't gain you any actual performance, because the hyperthreads have to continously switch the state of the one FPU.

However other threads in the system might gain a bit by the hyperthreads.

Blueberry wrote:
But because Logic's DSP code is heavily based on math, hyperthreading doesn't gain you any actual performance, because the hyperthreads have to continously switch the state of the one FPU.

Where did you get this info from? Have you tested it for yourself? If HT didn't help Logic any, then why do I see performance cut almost in half when I disable HT on a four core machine (going from 4 full cores + four HT cores down to just the four full cores)?

Firechild said in his post that *Logic 8* showed 16 cpu meters. At the time L8 shipped, no machine existed with that many cores, so I wouldn't be surprised if they tried to implement for future configurations but didn't get it right since no machines existed to test on.

At this point, however it worked in L8 is a moot point, it's not like they are going to release 8.0.3 with 16 core support.