Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!van-bc!rsoft!mindlink!a218
From: a218@mindlink.UUCP (Charlie Gibbs)
Newsgroups: comp.sys.amiga
Subject: Re: Lies, lies, they're telling us lies...
Message-ID: <760@mindlink.UUCP>
Date: 4 Dec 89 20:48:58 GMT
Organization: MIND LINK! - British Columbia, Canada
Lines: 62

In article <5003@nigel.udel.EDU> acm131@eric.ccs.northeastern.edu
(Craig Scott Lennox) writes:

>In Message-Id: <544@xdos.UUCP> Doug Merritt <doug@xdos.CCS.Northeastern.EDU>
>writes:
>
>> Ok, that said, he's not altogether wrong. But it should be rephrased:
>> "...*forces* you to write more modular code". Mostly :-) about that part.
>> There's nothing wonderful about being forced to break huge data structures
>> into smaller 64K chunks. Nor for code, for that matter.
>
>Well, according to the IBM rep, there *is*.  And this is one place where I
>couldn't figure out if he was giving me a line of crap or not.  But he said
>that segmented architecture makes multi-tasking more efficient, because to
>change context you merely reload the code, data, and stack segments. Instead
>of copying the entire contents of page zero, out and in, etc. etc.  Of
>course, whe I pressed him as to why 8 Mhz Amiga 1000's with 512K can
>multi-task better than his 33Mhz PS/2's he had no satisfactory answer,
>but still... for future reference, I'd like to know, is this a legitimate
>issue?

     He's giving you crap, whether he realizes it or not.  Change
context by reloading segment registers?  What about the rest of the
registers?  I know Intel doesn't like having too many registers,
but I can't think of very many programs which would appreciate
having their registers trashed by a context switch.  Of course, a
clever Intel salesman could argue that having fewer registers is
actually an advantage because there's less to save and restore :-)
but unless the 286 or 386 has an equivalent to the 68000's MOVEM
instruction I can't see much time being saved.

     Besides, a 68000 program which accesses things relative to
address registers uses those address registers the same way an
80x86 program uses segment registers, except that it's not limited
to a 64K segment size.  Heck, even Intel realizes that 64K segments
suck rocks; the 386 lifts that limitation, although it's too late
for MS-DOS victims.

     And speaking of crap, what's all this about shuffling the
contents of page zero?  What operating system does that as part
of a context switch?

     Bravo for nailing him on the multitasking capability.  Of
course, before OS/2 came along, there was always the stock IBM
answer: "If we don't have it, you don't need it!"  It'll be a while
yet before IBM devotees truly appreciate multitasking the way we
have been doing for four years now - but eventually they'll come
to enjoy it, and will remain forever grateful to IBM and Microsoft
for "inventing" it.

Flame off.

OBJ:

Q: What's the difference between a computer salesman and a
     used car salesman?

A: The used car salesman knows when he's lying.

Charlie_Gibbs@mindlink.UUCP
"I could never get the hang of ideology.  I do the rock, myself."
        -- Tim Curry