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View Full Version : Dual processors: a bad choice?


believo
Oct 20, 2004, 07:23 PM
I have heard arguments that dual processors aren't worth the cost and they should only be used in server enviroments. I've also heard that one processor is idle most of the time. What programs support dual processors and are these things true?
thanks

Logik
Oct 20, 2004, 07:59 PM
I have heard arguments that dual processors aren't worth the cost and they should only be used in server enviroments. I've also heard that one processor is idle most of the time. What programs support dual processors and are these things true?
thanks

i'm not too familiar with the mac.. but in a windows environment it is true that most of the time one processor is idle. this is due to the fact that most windows applications are not SMP aware. in other words they only work with one processor and not more. it could be different on a mac though and i'm sure someone will chime in. i bet most of apple's products use multiple processors, and apps like photoshop, dvd studio pro, final cut, etc... it has it's benefits its just whether the apps are written to take advantage of both processors.. since apple has been cranking out dual processor systems i'd think there'd be a good reason for it and i bet OS X takes good advantage of it, which apps do is nothing i know about specifically

Sun Baked
Oct 20, 2004, 09:16 PM
since apple has been cranking out dual processor systems i'd think there'd be a good reason for it and i bet OS X takes good advantage of it, which apps do is nothing i know about specificallyBasically it's quite a few of the Classic apps...

The new version of the OS (10.4) should really boost SMP capability, Apple is updating the kernal to a version of BSD with a lot of SMP updates.

---

In Mac OS X, the 2nd CPU really does make a difference -- if you use the apps that really take advantage of the 2nd CPU.

www.barefeats.com

Otherwise the 2nd CPU really shines as you start doing a bunch of user multitasking and running a bunch of programs at the same time.

7on
Oct 20, 2004, 09:26 PM
Many games are using the second CPU as a kind of "sound hardware processing" since Macs don't have hardware accelerated sound cards. Halo for instance, plays much much better on a Dual 1Ghz than a single 1Ghz with most other factors being the same.

And I'm sure Apple apps are MP aware. The OS definitely is (doesn't like, if you have one app open that's taking up 50% CPU and open up another app the OS does that second app on the 2nd processor or something?)

bousozoku
Oct 20, 2004, 09:35 PM
Since my system is busy, it's always taking advantage of both CPUs. I rarely see a slowdown because they're both active. I won't say that Mac OS X has the most efficient SMP but it works well enough to get me through the day effectively.

Blue Velvet
Oct 20, 2004, 09:44 PM
With Photoshop liquifying a 250mb file as Distiller chugs through a 6gb postscript file, Toast burning a DVD... playing iTunes and browsing around here all at the same time...

It just works beautifully & smoothly with 2 processors.

daveL
Oct 20, 2004, 09:50 PM
Take a look at Cinebench benchmarks. The one's I've seen show *much* better scalability on 2-CPU Macs compared to 2-CPU XP/2000 systems. Just as Billy Boy didn't think we needed more than 640KB of memory or a LAN (DOS days), he also didn't think we needed more than a single CPU (these days), so XP/2000 is misearable at threading and SMP.

As a data point, I can run ffmpeg on a dual G5 and get 1.5 CPUs, while the rest of the system (UI, networking, browser, burning a DVD, listening to iTunes, looking at photos, ...) respond crisply. On my wife's XP box I can't get any real multi-tasking; I burn a DVD using Nero and I'm hard pressed to get another App launched and working in a way I can use it. In fact, on her macine I'm *afraid* to try to do anything else for fear of blowing the burn. I've had that happen on XP, but never on OS X. In short, Unix/OS X was made for multi-tasking and, since the early 90s (not OS X), made for SMP.

I can tell you that I Fold twice as much with my G5 2.5DP than I would with a single CPU Mac.

Last, but not least, look at the cost delta. The new 1.8 GHz SP G5 PM is only 25% less (list) than the DP 1.8. Even if you were only getting 50% better performance from the DP configuration, you have a significantly better price/performance ratio. 'Nuf said.

Mechcozmo
Oct 20, 2004, 09:52 PM
Macs have supported up to 4 processors in desktops in fairly recent years.
I wish I had one of these, but with G5s (http://www.everymac.com/systems/daystar/mp_plus/genesis_mp932_plus.html)
DP machines tend to be 40% faster than a SP machine, but that is just an average. Overall, on a Windoze box, there ain't much dual processor stuff going on. In the Mac world, far more programs are being written to support DP machines.

angelneo
Oct 20, 2004, 10:02 PM
It seems that processors have been hitting a ceiling with the MHz, would we see a trend in using MP? imagine in the future, computers will sport 8 processors...hmm...

daveL
Oct 20, 2004, 10:29 PM
It seems that processors have been hitting a ceiling with the MHz, would we see a trend in using MP? imagine in the future, computers will sport 8 processors...hmm...
Dual core processors are here and quad core processors are on their way (IBM, Sun). It doesn't take multiple processors to benefit from SMP anymore. I think we are witnessing the latest snafu on the part of M$ and Intel. They just don't get it. Linux/Unix/OS X have been working and refining the multi-tasking and SMP aspects of their OS for *years*. M$/Intel just poked their heads up in the last 6 months and said: "Do they really need to scale to 2 CPUs?".

Meanwhile, folks buy WinTel 2-CPU boxes at a premium, not realizing they are getting maybe 25% more than a single CPU box. What a bunch of junk.

bousozoku
Oct 20, 2004, 11:12 PM
It seems that processors have been hitting a ceiling with the MHz, would we see a trend in using MP? imagine in the future, computers will sport 8 processors...hmm...

Considering that the hospital where I used to work ran on a dual PowerPC system where each processor ran at 77 MHz with 8 MB of L2 cache (!), I'm quite an advocate of multiple processors. We had around 200 terminals and PCs and around 75 printers attached to it and it usually went through the day just working smoothly. Of course, if you pay over $100,000 for an operating system, it's very efficient.

freiheit
Oct 21, 2004, 12:40 AM
I have often heard the comment (mentioned up above) that a typical dual processor system runs roughly equivalent to 1.5 times the speed of one of its processors (so a dual 2.0 is about like a single 3.0 or in my case a dual 1.25 is about like a single 1.8). This is, of course, a general rule. Some OSes (like the late 90's BeOS) are specifically coded so that the entire system and every program written for it make use of both (or all 4, etc) CPUs. BeOS on a dual processor system was often shown to run at about 1.8 or 1.9 times the speed of a single CPU. Linux was usually showing the 1.5 times rate (as I recall) and so was OS/2. Windows usually came in dead last simply because the OS and apps were not made multi-processor aware so only one CPU was in use most of the time.

In MacOS X I can only comment as a dual processor user -- I have never owned a single processor Mac. On the other hand, from a PC perspective I've only ever used single processors even when I had multi-processor aware software such as BeOS, OS/2 and Linux. My dual G4 1.25GHz runs very nicely. It boots up faster than my 2GHz Athlon based PC and, as mentioned before, I can be doing several things at once on the MAc and starting additional programs takes no time at all. On my (faster) Win2K uni-processor PC if I'm running anything complicated (video conversion, several concurrent downloads, etc.) my system can take ages to start a new program. MacOS X seems to handle multiple processors very nicely. I'm quite pleased.

LeeTom
Oct 21, 2004, 12:46 AM
To the guy up there bashing Windows' SMP support... Windows has supported up to 32 processors since Windows 2000 Server, and it does it pretty well.

Lee Tom

freiheit
Oct 21, 2004, 01:22 AM
To the guy up there bashing Windows' SMP support... Windows has supported up to 32 processors since Windows 2000 Server, and it does it pretty well.

Lee Tom

Windows 2000 did not exist in the late 90s that I mentioned. :)

Technically Windows has supported multiple processors since WindowsNT. But most Windows apps were written for Win95/98 which had 90+ percent of the Windows installed base but had no SMP capabilities. And now that one cannot buy a dual processor PC without buying the quite expensive Xeon or Opteron CPUs (P4 and AthlonXP/64 do not officially support SMP operation) it's impossible for me to judge Windows SMP support in the current releases.

angelneo
Oct 21, 2004, 01:25 AM
Actually it sounds quite logical given that now grid computing is powering so many super computers. If one battery cannot do the job, just bundle a bunch of them in series or parallel.

caveman_uk
Oct 21, 2004, 03:37 AM
I currently have a dual processor system. It seems the OS is multithreaded and is run across both CPUs evening the load. For individual apps it varies. Some are multithreaded and also spread the load others aren't and dont'. Even in these cases there is an advantage to having two processors. If one process - say ripping a CD or DVD - is maxing out one processor there is still capacity on the other processor so the machine still feels responsive.

So generally you don't really notice having dual processors until you really start loading the system or do lots of CPU intensive stuff at once. It depends on the cost differential and how heavily (really) you use your computer as to if it's worth it for you.

Bear in mind I don't think anyone's ever said the following two sentences...

1) I've got too many processors.
2) This computer is too fast.

daveL
Oct 21, 2004, 11:09 AM
To the guy up there bashing Windows' SMP support... Windows has supported up to 32 processors since Windows 2000 Server, and it does it pretty well.

Lee Tom
Compared to what, DOS? Windows has NEVER scaled well. Just because an OS *supports* 32 CPUs doesn't mean it uses them efficiently. Why do you think Linux has made such inroads in x86 server applications? I suppose if all you're doing with Win2000 server is running IIS (until it gets blown away by the latest worm/virus), you'll get 2+ CPUs worth of work done with a 4-CPU box. Try running Oracle on it and tell me how well it scales with 32 CPUs, before it crashes that is. Having worked at the enterprise level with big Unix metal for 15 years, during which I've displaced a lot of M$ crap for clients *specifically* because it wouldn't scale, I can tell you that your assertion above is nonsense.

J.Allen
Oct 21, 2004, 11:15 AM
Blah Blah Blah
Linux 64

any arguments?

daveL
Oct 21, 2004, 11:44 AM
Linux 64

any arguments?
Hmmm ... I'm not sure what your point is. Yes Linux, especially the 2.6 kernel, scales *much* better than Windows. Linux 64: Are you referring to 64-bit Linux or Linux scaling to 64 CPUs or ?? Anyway, Linux is good, as I believe I mentioned above.