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From: mash@mips.COM (John Mashey)
Newsgroups: comp.sys.super,comp.arch
Subject: Re: I/O subsystems
Message-ID: <39284@mips.mips.COM>
Date: 9 Jun 90 23:02:50 GMT
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In article <6583@amelia.nas.nasa.gov> eugene@wilbur.nas.nasa.gov (Eugene N. Miya) writes:

>I would say we are infatuated, or have a fetish on CPUs, and I/O will
>continue to be a problem.  So what is industry going to do about it?

1) I/O will always be a problem, for all of the usual design reasons,
and especially when working near the edge on peak performance.

2) However, I would suggest that it will start getting better, at least
in certain ways, and especially in price/performance.

3) The reason is the same kind of dynamic that has led to SCSI & Ethernet
chips, for example.  Specifically, when the time is "right", people are
induced to do fast, high-integration (and therefore fairly cheap) chips
that help solve parts of the I/O problem as well.

4) Consider, for example, Ethernet support.
a) Early on, Ethernet support was a board full of logic, not cheap.
However, since it was in a supermini, it was still a small fraction of
the price, so it probably didn't matter too much.
b) As microprocessor systems came along, Ethernet support is now down to
a LANCE chip or equivalent, and a little bit of glue:
	1) Workstations NEEDED cheap Ethernet.
	2) There was a market for large volumes, hence worth doing.
5) Same kind of progress in SCSI.

I would claim that the following dynamic exists:
1) Workstations and other micro-based products are zooming upward in
CPU performance at fairly low cost.
2) Such machines could certainly use better I/O.
3) The volumes make it interesting for people to design chips to support
such things, whereas this has seldom been true in the super- or mainframe
markets.
4) Over the next few years, we will see increasing interest in people looking
to sell support chips for:
	faster & wider busses
	I/O muxing & buffering
	network interfaces
	disk control, such as for RAIDs
5) There used to be huge numbers of different architectures for CPUs,
whereas now more people use CPUs, and design I/O systems.  In some parts of
the design space, it is easy enough to design computers with just a few VLSI
chips that include both CPU & I/O.  I think that space will enlarge to much
higher performance levels, as the faster VLSI CPUs make it both necessary
to get fast inexpensive I/O, and enough volume to make it interesting.

6) I'd still expect that supercomputers will have an edge in this area,
although I'd be amazed if killer-micros-with-(forthcoming better I/O)
don't blow them away on I/O price/performance basis (but not absolute
performance, of course).
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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