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Single core versus Multicore CPU

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Re: Single core versus Multicore CPU

Postby resistorman » Tue Dec 03, 2019 7:16 am

Single core FUD is being promoted by Intel since AMD is cleaning their clocks with multi core. Quite the reversal from the Athlon vs Core days.
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Re: Single core versus Multicore CPU

Postby Pete Kaine » Tue Dec 03, 2019 12:10 pm

JacoVanDuijn wrote:I have always thought that Multi-core CPU's where better (for Video editing, etc everything non-gaming related) for audio production. But I read that single core performance is better.

Which one is true?

Yes.

JacoVanDuijn wrote:And are their DAWS out there that make use of multi-core? (I read that in the new studio one 4.5 they support multi-core, but not how many. I wanted to ask this on the presonus forums, but I don't have Studio one to register).

Ok, so all DAW's have multi-core support and they are all core limited to some degree. I'd say thread limited, but as Eddy's already pointed out the true meaning of a thread is rather different from Intel or AMD's public facing definition which in reality is really what the rest of the world calls "Logical Cores" (as opposed to "Physical Cores").

I don't think there are any DAW's left out there that handle less than 48 LC's at this point and I suspect most will do a fairly standard 64 with a few more being able to be pushed higher, although I've seen perfomance start to deteriorate once I've gone beyond the 64 LC figure, so if anything I'd imagine the artifical constraints are to do with load balance managment although I suspect there are better people in this thread to comment upon that.

JacoVanDuijn wrote:I am about to buy a new pc and really don't know what to get. I was first going for the Ryzen 3950x, untill I read about the importance of single core performance.

Well, it's IPC (instructions per clock) that is key, or more to the point how accessible they are. You can have two chips with 4GHz core clocks, but the IPC on one might be twice as high as the other, so those two chips wouldn't be all that comparable this is the difference between an i7 first and tenth gen or a AMD first and third generation setup (figures pulled from thin air for point of the example).

Turbos can be miss-leading and the CPU to some degree is only as good as the weakest core.

They tend to stagger turbos, with one or two cores at the full figure and then each additional core being staggered by a 100MHz or 200MHz all the way down to that base clock. What this means is that if all cores are equally loaded, then it will start to lose data (discard and glitch the audio) when the slowest core runs out of overhead.

Of course, the system will try and balance it so that the weaker loads are on the slower cores in an attempt to get the most from the setup. Where this becomes tricky is that you tend to see the entire channel and even dependent tracks get processed on the same core in large chains. Maybe not such a great concern if your mixing in a more traditional sense of taking audio tracks and processing away, but the generation of audio in the box and the processing chains that get applied mean that you sometimes need to keep a careful eye on what a single core might be doing least it get bit overly demanding.

I've long been an advocate of trying to level the cores off where possible. My preference this is done around the single core turbo speed, but we'd raise the rest to match it and for instance with a 9900K we push all cores to 4.9GHz rather than just one of them.

Of course you can't always do this with every chip range as tolerances change between designs and the interesting one (well, headache inducing one in my case) has been trying to figure out where AMD stands on this.

They've been advising for a while now that RAM optimization is better for the end user than overclocking in any way and I agree, I got similar performance results out of overclocking and optimizing the RAM in recent testing, as I did out of overclocking the CPU to an inch of it's life, which means I didn't have to overclock the CPU and the voltages I cranked for that overclock could be removed and the chip now runs a lot cooler which of course is a great. The upshot of this is that you can either run slow RAM and overclock or your can run fast RAM and not overclock.

So, this means whilst we now have a cooler chip, we also open up the chances of it running out of performance earlier on a single core. In real terms through there is enough RAW performance through the extra cores that it more than makes up for this as a balance.

To note, AMD has come under fire for being able to rarely hit their advised turbo figures, with constant updates appearing to tweak it. Instead the 3950X for example (because it's fresh in my mind) has a 3.5GHz base clock and 4.7GHz advised turbo and in my own testing we're looking at it only managing to hit around 4.1GHz - 4.25GHz across the various cores. The interesting thing for me was that none of the cores were spiking under DAW usage (whereas they might with a program that favours single cores) and this is how I would prefer a CPU to behave when dealing with a hugely multi-core capable client and audio.

As a general example I would take a 12 core 4.2GHz over a 8 core 4.6GHz.
But I would most likely take a 8 core 4.6GHz over a 12 core 3.8Ghz

All depending on the generational IPC scores of course.

Eddy Deegan wrote:
JacoVanDuijn wrote:I have always thought that Multi-core CPU's where better (for Video editing, etc everything non-gaming related) for audio production. But I read that single core performance is better.

Are you sure you read that right? There may be advice out there to disable hyper-threading on certain Intel CPUs due to the issues associated with the various CPU hardware bugs that surfaced a while back but generally speaking more cores is better when it comes to video editing.

Video editing is largely off-line rendering and the CPU is able to just deal with it as and when it can free up the processing capability. More cores the better and we're not overly bothered by how fast they are (more is more through)

Audio (and to be be fair, video streaming) is real-time and so you either complete the work within a given cycle (i.e. your ASIO buffer) or you can expect drop outs and glitching to ruin your session.

miN2 wrote:Re Studio One: it supports multi-core, but they took serious time implementing it to a half-way decent standard in my view, and it still doesn't really hold a candle to the likes of Cakewalk and Cubase.

Studio One 3 by all accounts was pretty well put together, but from feedback the Studio One 4 engine managed to go backwards to some degree when they made changes under the hood. Apparently they've improved it again in recent build releases, so I'm a little bit lost to how exactly it holds up these days, although good to know they've been working on it.

merlyn wrote:The R9 3900x looks good with a slightly faster base clock of 3.8 GHz versus the 3.5 GHz of the 3950x.

The 3900X is marginally faster per core on average, but again we're talking about the system running a roughly 4.2 - 4.3 average across those cores under heavy loads. The small 100MHz difference for me puts the 3950X ahead on it's higher core count.

To anyone wondering why I've not published the 3950X yet, stock has been really lacking and I only got to play with one last week. I don't normally cover limited editions (hence no 9900KS coverage) and AMD isn't letting on if they are shipping any more stock anytime soon or at all. I'll more than likely cover it when I do the Intel 10 series, although they also don't have stock, but at least they can outline a figure of at last double digits when asked how many we might see over.
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Re: Single core versus Multicore CPU

Postby Folderol » Tue Dec 03, 2019 12:47 pm

As a point of interest, a certain soft-synth of my acquaintance has 1 very high priority audio thread, 1 slightly lower priority MIDI thread, and 3 very low priority UI and housekeeping threads.

In Folderol towers, on a single core machine it runs like a pig. On a dual core one it runs well. On a 4 core one it runs extremely well. The 4 core machine runs at the same clock speed as the 2 core one (neither overclocked).
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Re: Single core versus Multicore CPU

Postby JacoVanDuijn » Sat Dec 07, 2019 5:12 pm

Pete Kaine wrote:
To anyone wondering why I've not published the 3950X yet, stock has been really lacking and I only got to play with one last week. I don't normally cover limited editions (hence no 9900KS coverage) and AMD isn't letting on if they are shipping any more stock anytime soon or at all. I'll more than likely cover it when I do the Intel 10 series, although they also don't have stock, but at least they can outline a figure of at last double digits when asked how many we might see over.

Dear Pete,

thank you for taking the time and writing all of this. I have learned so much from you and others here.

1. Let's say I would get a good SSD, good and fast ram etc, so no bottlenecks and I have the money should I go for the 3950x? My aim is to decrease stutter and crackling. Will the 3950x be the best option of all the cpu's out there or would you advice a different CPU?

2. You also talked about real-time. is it true that real-time processing is done better with more cores (again, assuming no bottlenecks from other PC parts)?
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