umnoor@ccu.umanitoba.ca (Nasir Ahmed Noor) (06/14/91)
I am posting this also in *.advocacy. Maybe I will get a simpler explanation
here, that I can understand.
I was argueing with my friend about the subject of multitasking. His explanation of multitasking is:
THEORY=="Multitasking uses registers. M*tasking can not be FASTER on one
computer than the other because of the way it works on any platform.
There are 100 registers available. Two programs require 50 registers
each so they can both execute at the same time. If one requires 60
registers then the other has to wait for the first to finish. My
friend said it does not matter if you m*task using amiga or system 7.0
this theory is true for both so the amiga can not m*task faster than
7.0 when running identical programs."
I have VERY little knowledge of the techniques required in multitasking so I
could not refute his theory. I would like to be able to say that amiga will
multitask faster/better because it was built around that concept and the mac
is programmed to do multitaskin. I would like to challenge his theory.
I have some knowledge of task priorties and delegating the task of graphics
display and memory transfers to the custom chips. This should have some effect
on the speed of execution.
I think he might be mixing memory with registers.
Please no specific replies. I want to know how the two sides compare in
GENERAL.
TAI!!!!!!!!!
{using his own account to gather ammunition}cg@ami-cg.UUCP (Chris Gray) (06/16/91)
In article <1991Jun14.154041.15151@world.std.com> awm@world.std.com writes: [stuff about register save/restore deleted] >> I think he might be mixing memory with registers. > >This seems likely. Unless you have virtual memory, you can only run as many >applications as will fit in main memory. However, most machines these days >have enough space for a large number of applications to run at once, and >the speed at which you can switch between them definitely depends on the >operating system. Another significant factor is how much of the operating system state needs to be saved/restored on a task switch. Since the Amiga's Exec was designed with task switching in mind, this is a relatively simple affair (not much more than moving a couple of pointers). I recall reading an old article in Byte, however, that said that one of the problems that MultiFinder has is that the Mac's OS has a LOT of state that has to be manually preserved when switching tasks. Basically, anything that is task-specific and at a fixed location must be entirely copied out and saved, then the stuff for the new task copied back in. Mac guru's could likely expand on this. It really doesn't have too much effect, however, unless you try to switch tasks too often. If the switching is at a human speed, you won't likely notice it on a 68020 or higher. At 100 times a second, you might. -- Chris Gray alberta!ami-cg!cg or cg%ami-cg@CS.UAlberta.CA