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From: lindsay@gandalf.cs.cmu.edu (Donald Lindsay)
Newsgroups: comp.arch
Subject: Re: Fast I/O
Message-ID: <13096@pt.cs.cmu.edu>
Date: 18 May 91 05:28:40 GMT
References: <97b302n807vo01@JUTS.ccc.amdahl.com>
Organization: Carnegie Mellon
Lines: 29

In article <97b302n807vo01@JUTS.ccc.amdahl.com> 
	haw30@DUTS.ccc.amdahl.com (PUT YOUR NAME HERE) writes:
>>>Also, is there anything to prohibit a RISC based machine from having a high
>>>speed IO subsystem?
>    The HIPPI? interface with RAID (Redundant Arrays of Inexpensive Disks)
>disk systems is one possible solution.

The Amdahl rule (1+ Mb/s, sustained, per MIP) suggests that the push
towards 100 MHz processors is also a push past 100 Mb/s. The most
desirable kind of I/O is network I/O: so, FDDI rates seem inevitable,
with heart's desire somewhere beyond.

A project here is building a gigabaud LAN. With that LAN, the RAID
disk farm can be down the hall: no problem. 

The big fiber-and-laser push by telecom companies has made the
network side entirely possible (at a price which will, we hope,
drop). A rather less tractable problem is connecting the network to
the RISC machine(s). For instance, there are machines which boast a 
4 MB/s VMEbus interface, and that just doesn't mesh well with an
80 MB/s firehose. Those machines have to drink through a straw.

Not surprisingly, the net will talk to the nearest Cray and Maspar
over HPPI. With all respect to HP, I didn't hear plans for an EISA
interface.


-- 
Don		D.C.Lindsay 	Carnegie Mellon Robotics Institute