Dual-Core/Multi-core CPUs -- The Hype and Reality

[amirm]

As promised, here is an article on multi-core CPUs.

Multi-core CPUs and Performance Considerations.

As always, questions, spelling and grammar corrections appreciated .

 

[DonH50]

Highlights the biggest problem I (and presumably others) have seen: too little SW actually uses the extra core(s)! Leaving us with a drop in performance for a newer PC having more, slower cores... The multithreaded/parallel compilers are apparently still few and far between...

I thought Win Vista/7 was supposed to take advantage of the extra cores for multiple applications by running in their own processor space? I am still running XP so do not know, though I have a couple of Vista and one Win7 machine in the house (wife and kids so I never see them unless they break)...

 

[amirm]

Thanks Don. I wanted to address your point above but forgot in the article .

All modern operating systems utilize the extra cores as you state whether it is older XP or MacOS. This was supported when "mutiprocessing" was added to the operating system.

So to the extent you run multiple CPU intensive application at the same time, you do utilize the extra core. Alas, if you start perform you see that your cores are all idle. In typical desktop workload there just isn't that much CPU usage to keep one core busy let alone two.

The feature that was added in Win 7 was to help with power management. Instead of constantly keeping all the cores busy with little work here, and little work there, the OS attempts to concentrate more of the workload in one CPU and hence let the CPU shut down the other cores to save power. This I believe also increases the chances of Turboboost kicking in.

 

[DonH50]

Ah, got it. I am not running any native multiprocessor applications now and rarely enough apps to use the extra cores. I should test with a couple of CPU-intensive programs (e.g. run a Spice simulation and then fire off a Mathcad worksheet) and see what happens...

I do notice that some apps (Webroot comes to mind) drag (perceived, as in response to mouse/keyboard) performance way down when they are running...

 

[microstrip]

Amir,
After reading the article I asked my son at lunch time about his opinion on multicore processors and he his a multicore adept - he says that MATLAB and Simulink take advantage of multicore processor systems.

So it seems it is not "bad news" for everyone!

 

[amirm]

Oh definitely. Compute intensive in the industry abound. Applications like Finite Element Analysis used for optimization of material science in making everything from cars to bicycles and CFD work that Keith does for room acoustics can utilize all the cores they can get. Those folks are happy as I am when editing photos . The issue is the mass market customer who keeps thinking more core is better yet does not have a workload that utilizes them.

The other issue is the fact that we are forced to buy them whether we need them or not. I love to see a CPU with one core at 60% of the cost. But like bundled cable programming we have to take it all even if we don't need it all.

 

[Nicholas Bedworth]

My recollection is that Windows in its current form is optimized in anticipation of 16-32 cores; it really loves large numbers of CPUs, and performance scales very well, compared to earlier OS.

I believe that the speed Windows 7 on 8-16 cores is roughly the same as the very-fast Windows XP on dual cores of a few years back. Amir may remember the details, but it's something like that.

One thing for sure, the overall performance of, say, a cheap $1000 HP quad-core, hyperthreaded to 8, laptop leaves nothing to be desired. I'm sitting here bringing in data at 120 MHz over Ethernet, processing it in real-time for phase noise, and streaming video, typing away, etc., and the overall CPU usage is, ahem, 25%.

Somehow there's nothing more satisfying than watching a computer really slaving away with heavy CPU and I/O utilization. Normally they're watching us slave away.

 

[FrantzM]

Hi

The apparent speed with which today's laptop acquire themselves of some tasks is not necessarily due to their multi-core processor.. Really very few a[[lications are optimized, even less OS...

Modern days PCs and laptops are faster because of a few other reasons among them :
Better graphic processors. Graphic cards are equipped witht hteir own processor and their own substantial amount of RAM. The CPU is free from running graphic in today's PC and laptops. The Biard are mini-computer themselves with substantial horsepower.
Faster buses we are from the 133 MHz of 10 years ago
Faster memory 1333 MHz os commonplace in RAM
More RAM, any personal computer , portable or not worth its grain of slat has 4 GB or more ,,,
Faster peripherals SATA is faster than PATA and any computer produced these days has SATA disc, more rarely SCSI.
boards are powerhouse in their own rights. it is not uncommon for graphic cards to The CPU is for all practical purposes delested of graphical concerns ( a very heavy valculationsand much more available RAM. Any laptop one buy is likely to have 4 GB or more of RAm plus the graphic cards are much more powerful than before. s the processor(s) has/have much less to process and wait much less because the pagination (writing stuff on disk because it would not fit on available RAM) is reduced.

It would surprise many to see how seemingly old clunkers, say a Pentium III (don't laugh) processor-equipped PC with vast amount of RAM, say 4 GB with, Solid State Drive and good graphic card, becomes .. it may not challenge a new machine with the usual configuration (lot of RAM. fast SATA disks , etc) but fast it becomes and will keep up..

 

[Orb]

Also worth noting it also includes how the internal architecture of processors improve for the better (how they deal with various commands and use of L1 and L2 cache as an example).
Even without the use of both dual cores, the latest processor is still faster than the previous processors that have a higher speed (to a certain extent) when they are compared for performance in general applications and also games.
That said comparing like for like the best to buy is the highest processor speed instead of more cores if one knows apps and OS are not making use of more than one core and one is looking for the best performance (not necessarily the right choice in the context of audio use).

Cheers
Orb

 

[WDB]

Some programs get a huge boost in performance from the video card, I have 3D graphics software that takes advantage of Nvidia GPUs to render animation or stills much faster than the CPU can do it alone. Video encoding is also an area that is seeing big gains by using the GPU. More info here. http://developer.nvidia.com/category/zone/cuda-zone

 

[amirm]

That is true. But the number of apps that can do that is incredibly small. Graphics companies had been making the claims of acceleration for a long time but it was not true until recently. The problem is that the CPU can act on its data in main memory instantly. It is there for it to use. To have the graphics card operate on it and efficiently so, you had to ship that data to it, have it crunch, and then send it back to main memory for the CPU to use. That roundtrip defeated any boost in performance that the GPU provided. So unless the work being done was very complex, it was actually slower to offload things that way. So the trick is to have the GPU handle everything. This is what is done for example in video editing where the entire effect pipeline can be put in the GPU now (assuming you have gobs of GPU memory) and then run it there.

 

[WDB]

The number of programs taking advantage of GPU acceleration will be increasing, for now the types of programs that can most benefit from it are the ones that have it now or will soon, to be honest most people don't need anywhere near the power of todays computers.

 

[Bruce B]

That's why I like Pyramix MassCore as well. You can assign 1-3 cores specifically for this software and Windows doesn't even see them. You can bring up Task Manager and only the remaining cores are visible.