Thread

Pre Emptive Multitasking in Classic

68kMLA 68k 17 posts Aug 31, 2009 to Sep 2, 2009

#1 Mon, 31 Aug 2009 - 05:43 68kMLA

Does anyone remember the control panel Respond? I found a download for it, http://download.cnet.com/Respond/3000-2094_4-3836.html

Its supposed to provide limited pre emptive multitasking to System 7 on up. Its also known as red shed threads and I belvieve I found the source code to it here,

http://rentzsch.com/trac/browser/trunk/Carbon?rev=88

#2 Mon, 31 Aug 2009 - 07:24 68kMLA

The standard ThreadsLib from Apple provides pre-emptive multitasking on 68k and it's a standard part of the operating system.

Programs have to be written to use it, and most of the operating itself will collapse in a heap if you try calling from pre-emptive threads.

#3 Mon, 31 Aug 2009 - 07:41 68kMLA

@porter, sounds like 'the manager' for gs/os althought blended with multifinder a bit.

#4 Mon, 31 Aug 2009 - 18:16 68kMLA

what is pre-emptive multitasking?

#5 Mon, 31 Aug 2009 - 19:28 68kMLA

That's where an over-lord (the OS) decides how long each task is going to be able to run for. Contrast this to co-operative multitasking, wherein each task must specifically give up time to the next task.

#6 Mon, 31 Aug 2009 - 19:33 68kMLA

It's something the Amiga had long before MacOS

#7 Mon, 31 Aug 2009 - 19:46 68kMLA

That's because the Mac was keep it simple, stupid and only had 128k.

#8 Mon, 31 Aug 2009 - 20:46 68kMLA

Porter I was under the impression that the standard threadlib was only co-operative multitasking.

#9 Mon, 31 Aug 2009 - 21:59 68kMLA

Porter I was under the impression that the standard threadlib was only co-operative multitasking.

One 68k ThreadsLib happily supported pre-emptive multitasking. But you had to play the game and could only call interrupt safe MacOS APIs, which ruled out QuickDraw and anything that allocated memory. You could do plenty with device and network drivers.

On PowerPC they dropped the idea because it fell into the too-hard basket when you also had to include the mixed-mode-manager.

#10 Tue, 1 Sep 2009 - 05:06 68kMLA

That's because the Mac was keep it simple, stupid and only had 128k.

Yeah the amiga did it in 256kb in the a1000 in '85.

In sooo much ram!!!

#11 Tue, 1 Sep 2009 - 05:38 68kMLA

Intel did pre-emptive multitasking on the lowly 8080 back in 1980.

#12 Tue, 1 Sep 2009 - 06:34 68kMLA

Intel did pre-emptive multitasking on the lowly 8080 back in 1980.

how? you have my interest,

was it with M/PM ? - would that have been dri?

#13 Tue, 1 Sep 2009 - 09:08 68kMLA

At the end of the day, such a control panel is not of much use without a rewritten Finder that's designed to take full advantage of pre-emptive multitasking. I have downloaded Respond, will give it a try in System 7.1 on my LC 475 soon.

#14 Tue, 1 Sep 2009 - 09:51 68kMLA

was it with M/PM ? - would that have been dri?

No, iRMX.

http://en.wikipedia.org/wiki/IRMX

#15 Tue, 1 Sep 2009 - 11:23 68kMLA

I think I once ran NetBSD on an old Classic II (I think it needs a 68030). NetBSD gave the machine full pre-emptive multitasking. Shame it did away with the GUI and couldn't run any Mac software though.

#16 Tue, 1 Sep 2009 - 18:20 68kMLA

NetBSD .... 68030. Shame it did away with the GUI

NetBSD support X-Windows and your choice of OpenMotif, GNOME, KDE or whatever.

... and couldn't run any Mac software though.

It never claimed it would. :

#17 Wed, 2 Sep 2009 - 09:39 68kMLA

NetBSD support X-Windows and your choice of OpenMotif, GNOME, KDE or whatever.

I should have explained myself better... this was back in 1997, NetBSD for a 68k Mac didn't have the same "bells and whistles" as its x86 counterpart. It was pretty much a bare bones *nix OS. Seemed really weird seeing white text on a black background on a Mac.