Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!usc!apple!mips!mash
From: mash@mips.COM (John Mashey)
Newsgroups: comp.arch
Subject: Re: Evans and Sutherland quits the superbusiness
Message-ID: <32146@winchester.mips.COM>
Date: 26 Nov 89 03:28:24 GMT
References: <1128@m3.mfci.UUCP> <1989Nov22.175128.24910@ico.isc.com> <3893@scolex.sco.COM> <39361@lll-winken.LLNL.GOV> <3898@scolex.sco.COM>
Reply-To: mash@mips.COM (0000-Admin(0000))
Distribution: usa
Organization: MIPS Computer Systems, Inc.
Lines: 32

In article <3898@scolex.sco.COM> seanf@sco.COM (Sean Fagan) writes:
>In article <39361@lll-winken.LLNL.GOV> brooks@maddog.llnl.gov (Eugene Brooks) writes:
>>In article <3893@scolex.sco.COM> seanf@sco.COM (Sean Fagan) writes:
>>>most "killer micros" is defficient because I can't do *real* DMA (it tends
>>>to steal cycles from the CPU).  (N.B.:  some K.M.'s *do* have *real* DMA.
>>>I'm waiting for them to come out with *real* I/O subsystems [using, say, a
>>>68000 as a PP].  Then they will scream, even compared to a Cyber.)

Just to correct a potential mis-impression:

a) Since 1983 (or earlier, in a few cases, I think), anybody seriously
building multi-user systems / servers from microprocessors has tended to
build at least the high end of a product range with micros [68K, 186s,
Z8000s, V-??, etc] as I/O processors.  Some workstations [Sony News,
for example] have 2 68Ks, one as an I/O processor.

b) Although one may choose to use a "Killer Micro" in a workstation/PC/cheap
server architecture, where there may be only one path to a memory bus with
SIMMs, or similar design:
	1) It usually has DMA.
	2) it usually has a cache, and so I/O has some impact, but is hardly
	what people used to call cycle-stealing (where every I/O stopped the CPU	almost cold).

c) Any "Killer Micro" aimed at larger server/multi-user designs (as opposed to
least-cost designs):
	has DMA
	usually has CPUs in at least some of the I/O boards, where appropriate
	sometimes has multiple paths to memory, i.e., a VME I/O bus and a
		private memory bus

d) Many of the current high-performance I/O boards have 68020s, already,
as in some of Interphase's products.