Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!mailrus!uunet!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.arch
Subject: Re: Killer Micros and vectorized code
Message-ID: <10272@cbmvax.commodore.com>
Date: 20 Mar 90 20:08:19 GMT
References: <00933EBB.E972FCA0@KING.ENG.UMD.EDU> <51771@lll-winken.LLNL.GOV> <100598@convex.convex.com> <52661@lll-winken.LLNL.GOV> <1990Mar19.234839.13829@Neon.Stanford.EDU>
Reply-To: daveh@cbmvax (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 45

In article <1990Mar19.234839.13829@Neon.Stanford.EDU> philip@pescadero.stanford.edu writes:

>Predictable response time...This is also (one of the reasons, anyway) why
>Apple does not support pre-emptive multi-tasking. 

Pre-emptive multitasking has nothing at all to do with predictable response time.

>I'm using a 16Mbyte DECstation 3100 and despite the faster processor, it doesn't compare 
>with a 68030 Mac on user interface reponsiveness. And the DECstation is hardly ever
>used by other users. 

The way UNIX implements its multitasking has everything to do with the
unpredictable response time you get on UNIX workstations.  Same reason the
NeXT box has a "jumpy" feel to the user. 

I use two non-UNIX systems with pre-emptive multitasking -- Apollos (under
Aegis, or DomainOS, or whatever they call it these days) and Amigas.  Both
of these systems, especially the Amiga, are extremely responsive.  In fact,
moreso than the Mac.  For example, on the Amiga, the main things governing
user-interaction, such as mouse and keyboard response, are interrupt driven
and managed by a high priority task.  The user interface also runs at a
higher priority than the average user task.  So when you start that 64k x
64k spreadsheet to recalculating, you don't have the mouse drop dead, and
you can still move windows around. 

What makes the difference is real time response, an operating systems
issue, but not the same thing as pre-emptive multitasking. 

>Moral of the story? A multi-tasking OS with virtual memory etc. has its price. 

The real moral of the story is that operating systems originally designed
for multi-user operation with users hooked in via serial line text
terminals may not provide the best feel when adapted for use as the
operating system for GUI based, single-user workstations.  At least not
without a great deal of rethinking, which apparently hasn't yet been
completed by most of the folks building these systems. 

>Philip Machanick
>philip@pescadero.stanford.edu


-- 
Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
                    Too much of everything is just enough