Path: utzoo!utgpu!watmath!att!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!ncrlnk!ncr-sd!hp-sdd!hplabs!hpfcdc!hpldola!hp-lsd!prisma!mo
From: mo@prisma
Newsgroups: comp.periphs
Subject: Re: ESDI and SCSI2
Message-ID: <8100003@prisma>
Date: 3 Aug 89 12:49:00 GMT
References: <252@marvin>
Lines: 16

Sorry, but even on a Sun 4/280 you can get lots more through the
machine than the disks can readily currently support, particularly if
you tweak the system a bit.  Amdahl's law says you need 1 megabyte
per second of disk bandwidth per MIPS for a balanced system.
Now I know much of the world is currently enamored with the MIPS
rating of a machine as the only performance number, but a 20 MIPS
cpu that has 2-4 MBs/sec of I/O is pretty unbalanced for some jobs,
and as 20 goes to 200, it becomes untenable.

Just remember that spinning the processor isn't the only thing computers
get paid-for to to.  In lots of jobs, I/O is a Big Deal, and you
certainly don't have to use 35ns static rams for main memory to be
able to do I/O (although you *will* have to build a real
memory system).

	-Mike