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tobster May 3, 2001 08:55 AM
I just had a conversation with somone that said that he could never use mac os 9 since it has no multitasking. That it was inferior to windows 2000 (not 98) for this reason.
Now, what I want to know is what is multitasking. Doesn't OS X have it?

Jsnuff1 May 3, 2001 02:23 PM
search the fora, there are plenty of long threds on this topic, in short multitasking is the ability for the OS to use multipul cpu's
Proteous May 4, 2001 02:34 AM
Multitasking is not being able to use multiple cpu's but the ability for the OS to do multiple things at the same time. Mac OS 9 is not a true multitasking OS, OSX is though. With OS 9 the programs themselves get to deside how much processor time they want to use. With a true multitasking OS the OS gets to decide how much processor time each program uses. Like Jsnuff1 said you can find a better explination elseware in the forums. Windows 2000 is a multitasking OS, although that doesn't mean that it's better. ;)

-There are three types of people, those who can count, and those who can't.-
Cipher13 May 4, 2001 04:09 AM
Very basically, the "frontmost" application gets all the processor time it wants, while other apps behind it slow down. Often it means if one app entirely hogs the proc, you can't do anything else at all.

OSX's multitasking is awful - Windows 2000's is much better.

Oh well. It'll improve "in time" :\


AIM: Cipher1387
ICQ: 48111606
Milio May 4, 2001 09:33 AM
OS 9 does indeed have multitasking. If you can run two or more programs simultaneously, then you are multitasking. That's all the word means.

Now, there are different technical ways to handle running multiple programs at once. The Mac OS uses something called Cooperative Multitasking. Like it was described above, that basically means that the applications cooperate with the user and each other by understanding that the one the user is currently using gets the most CPU time. This is an oversimplified description--there's a lot more going on behind the scences--but it will suffice.

OS X uses something called Preemptive Multitasking. This allows background processes that need to do something to preempt CPU time from other apps in order to give itself more processing time.

Preemptive multitasking is generally considered superior to cooperative multitasking. With most users, even though an app is frontmost it might not need much CPU time. For instance, you could just be sitting reading a web page. In a cooperative scheme, that frontmost app that's not really doing anything is hogging the CPU and keeping other apps from running at full speed. So if you were burning a CD, you wouldn't want to do it in the background. But on a preemptive system, it would know to give that CD burner in the background enough time to actually work and not make a coaster. The downside to preemptive multitasking is that the more applications that are running, the slower the system overall. And seriously CPU heavy tasks in the background can make frontmost apps sluggish.

Basic OS implementations:
Mac OS 9: Cooperative Multitasking
OS X: Preemptive Multitasking
Windows: Preemptive Multitasking

From my own user perspective, Windows seems to do a better job than either Mac OS 9 or OS X. That's not a technical evaluation, just an opinion from use.
Cipher13 May 4, 2001 01:58 PM
Yeah, I'll agree with your assessment, Milio - Windows multitasking is very very good.

OSXs is quite bad - but, I admit that is probably due to the fact that I have only 128 megs of RAM. But, that SHOULD be plenty

And OS9's? Well, I've learnt to use co operative multitasking, so I like it - but thats not a fair assessment... ahh well.

Windows multitasking is cool.


AIM: Cipher1387
ICQ: 48111606
Milio May 4, 2001 07:45 PM
Originally posted by Cipher13:
OSXs is quite bad
I don't know from a technical viewpoint if it's good or bad. But I do know that on a beige G3 with 190MB RAM that running 3 simple apps noticeably bogs down the system.
Randycat2001 May 4, 2001 08:35 PM
Your explanation seems good overall, but I would like to clarify the "browser while burning a CD" scenario you gave. I was doing just that in MacOS9.1 last night, and everything went fine (granted, I wasn't pushing it too hard for the very reason of avoiding any stalls to the burner, but the CMT did stand firm to its job as I was browsing in Netscape and iTuning a CD to a USB CDR drive). There's a lot of ways that CMT can fall short, but given good software support, it still manages to get the job done just fine. (Just wanted to give CMT a little credit for something one would not normally expect it to pull off.)

[This message has been edited by Randycat2001 (edited 05-04-2001).]
Milio May 4, 2001 09:39 PM
Randycat, I'm interested in how you got this to work for you. Does your burner support something like BurnProof? Also which burner software do you use? And what is the interface (usb, firewire, atapi)?

I can barely get a usb burner to work reliably in the foreground with the Mac.
Randycat2001 May 4, 2001 10:41 PM
I was using a USB ZipCD, iTunes 1.1, I have the Mac OS USB authoring extensions enabled and not the Toast ones, and I'm using Netscape (in pictures off mode). I'm using OS9.1 with VM on, lots of stuff open (even VPC, but I keep it in the background only while burning), and currently run 384 MB of RAM on a BW G3 350. I think the ZipCD has a 2 MB cache which would be a form of "burn-proof" measure. I also use the Apple Disc Burner, instead of Toast for burning data CD's. I really enjoy the multitask access that iTunes and Disc Burner supports (the Toast pack-in software blocks out access once in burn mode, which I don't like, but I presume this is for enhanced "burn proofing").

It's possible that running with images off in Netscape helped to minimize the browser load so the CD burn didn't get interrupted too much. If you are loading images over a dial-up, I imagine this could cause intermittant resources for the burner process. I've never tried to mess up a burn in this way, though.

The ZipCD never seems to burn at full speed, though. It just plods along at around 2x speed. I don't mind, since I still have access to the computer if I wish. I imagine if you have a drive that wants to burn at higher speeds over an IDE, SCSI, or firewire it might become data starved more easily, so CMT timing could be more critical.

Let me know if you need more info on my setup, and by all means let us know what you have running. Feel free to start a new topic to avoid derailing this topic.
Jsnuff1 May 5, 2001 10:41 PM
my bad, sorry for the confusion i was thinking of Symmetric multiprocessing
Mac_Nacho May 11, 2001 08:52 AM
Now a question. Why Mac OS has this kind of "reputation" to be more stable than windows?
Does windows 95/98 have protected memory?
What are the implicances of having preemtive multitasking and NOT having protected memory?'-->instability?
Cipher13 May 11, 2001 09:29 AM
Originally posted by Mac_Nacho:
Now a question. Why Mac OS has this kind of "reputation" to be more stable than windows?
Does windows 95/98 have protected memory?
What are the implicances of having preemtive multitasking and NOT having protected memory?'-->instability?
Yeah, Win has protected memory... dunno 'bout 95/98... I'm talking 2000...

Having pre-emptive multitasking and not protected memory is juts like... having apples and not bananas. They go nicely together, but one is just the same as ever without the other...

AIM: Cipher1387
ICQ: 48111606
chumley May 12, 2001 02:48 PM
Cipher wrote:

"OSXs is quite bad - but, I admit that is probably due to the fact that I have only 128 megs of RAM. But, that SHOULD be plenty..."

I agree, it should be plenty, least RAM is getting cheaper by the minute (just saw lifetime guaranteed PC 133 CL2 2-2-2 that works at CL3 for current firmware rev compat. for 144.00/U.S.)...

I work with a developer, and just attended one of Apple's Mac developer OS X "kitchens"; basically giving us the "not for public consumption" roadmap/411 on OS X. Granted, there's a fair amount of PR bs circulating at these things, but had a chance to speak with some VERY plugged-in OS X developers/testers.

Bottom line for pre-emptive multitasking in OS X is that, since RAM aloocation to both the OS and apps is now dynamically allocated, as is VM, that the more RAM you can throw at a multitasking environment in OS X, the better. If I were to compare it to Win NT/2000, I'd have to handicap Wintendo for its greater maturity, greater R&D budget, and its fundamental crutch- its foundation in DOS, a language with all the complexity of Unix and (very) little of the power.

As for Protected Memory and Pre-emptive Multitasking- it's kind of like having a great girlfriend that likes sex as much as you do, rather than one who's considering the Nunnery...ok, bad analogy, but-

you can't actually utilize the full power of Pre-emptive Multitasking without Protected Mamory. PM allows each process and/or app function/task to take place in its own "back yard", for lack of a better metaphor, and if it falls to the ground in its tasks, it won't get run over, like it might if it played in the street (Pre-Emptive Multitasking w/o Protected Memory) Multitasking refers to CPU time/priority on CPU's "To-Do list; Protected Memory insures that each task/app/process/ has its own "space" in which to accomplish its individual goal.

OS X will, to display my iron grip on The Obvious, continue to mature and extend its capabilities. I hope it's sooner rather than later; my information from various sources indicates that sooner might just win...


Paul Crawford May 14, 2001 10:42 PM
Hi all,

For those who're keen on lower-level perspectives on this topic, there's also an ancient related Why is MacOs not good at Multitasking?(compared with NT or 2000) thread in this Forum which you might find of some interest...

The thread also includes a side-debate on the multitasking merits of Java 1 on Mac OS (Classic, as X was still a fairly distant blip on the horizon then), if any. The debate was never really resolved, but perhaps it doesn't matter now that there's Java 2 on Mac OS X...

Regards, and happy tasking [of whatever kind ;-)]


[This message has been edited by Paul Crawford (edited 05-14-2001).]
Randycat2001 May 14, 2001 11:36 PM
Hey, I just did the ultimate (in my mind, that is) where I was Discburning a CD in the background while doing some 3D modeling operations in VPC and surfing the internet. I could have added an MP3 import in iTunes on top of all that, but I thought that would be pushing it (maybe next time The CD verified OK. I'm surprised it worked, but it did!
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