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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Why VM? (was Re: New Macintosh Strategy)
Summary: VM not the only way to get multiprocessing...
Message-ID: <10444@milton.u.washington.edu>
Date: 1 Nov 90 23:06:31 GMT
References: <1990Oct30.075308.15261@world.std.com> <1990Oct30.093218.12931@d.cs.okstate.edu> <=V8%9Z$@rpi.edu>
Distribution: comp.sys.mac.hardware
Organization: University of Washington, Seattle
Lines: 30

In article <=V8%9Z$@rpi.edu> Garance_Drosehn@mts.rpi.edu (Garance Drosehn) writes:
>Most people who will be buying a low-cost mac do not need VM.  If they 
>can't afford a few more megabytes of memory at $40 a megabyte, then they 
>aren't likely to be able to afford the extra cost of a 68030 or a PMMU, 
>plus the cost of the larger hard disk that is needed.  Besides, I'd rather 
>use RAM (with no moving parts) then increase the wear and tear on my hard
>drive.
>
	Damn straight.  Four SIMM sockets allows 16Mbytes (with 4M DRAMs)
right now on SE/30's.  Our VAX with 12Mbytes had entire DAYS of operation
in which up to forty users satisfied their virtual memory needs ENTIRELY 
from cache (i.e. NO disk access, NO true virtual memory use).  The
multiuser environment requires some strange things: fast disk access
times/transfer speeds; memory recovery as processes depart; large numbers
of I/O ports with overflow protection.
	The PC environment makes ALL these things unimportant.  Bigger
memory can give me three more megabytes on my Plus; virtual memory
can't ('cuz I don't have that much disk space available right now).
With some exceptions (Mathematica), memory size for applications is
entirely satisfied without virtual memory support.
	That said, I should also point out that if Apple ever comes
up with a complete line of machines with VM, they can do things
for file handling and runtime library support that will make the
system look like a bag of magic tricks, and retire most of the 
Resource Manager's software hooks (which give program developers
a LOT of typing exercise...).  In time, I expect VM will be required.
Maybe when System V10 is ready, all our sub-68030's will be
obsolete.  2005 maybe?

 I am known for my brilliance,                 John Whitmore
by those who do not know me well.