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From: craig@BBN.COM (Craig Partridge)
Newsgroups: comp.os.research
Subject: Re: Extremely Fast File Systems
Message-ID: <5555@darkstar.ucsc.edu>
Date: 30 Jul 90 22:11:47 GMT
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In article <5512@darkstar.ucsc.edu> lm@snafu.Eng.Sun.COM (Larry McVoy) writes:
>
>Why not: CPU speed
>------------------
>
>A Sun 4/490 is a reasonably fast machine.  Moving I/O requires a copy.
>The 490 has copy hardware that maxes out at 25 MB / sec in the kernel
>and 14 MB / sec in user space.  

Larry:

    I've heard the discussions about busses and disk drives before
but this is the first time someone's said CPUs will be a problem.

    Mostly I've heard the reverse argument -- CPUs are gonna gobble data
as fast as the network and disks can feed it.  For example, several researchers
are muttering about 250 MIP CPUs in the next couple of years -- one person I
know at DEC is talking about a 1 BIP workstation by 1995.

    Those CPUs will have modest memory caches that run at CPU speed --
so close to the CPU you'll have a system chomping on gigabits of data
per second (consider a 32-bit instruction with one 32-bit memory operand
 -- thats 250 MIPS * 64 bits = 16 gigabits/second of data flowing through
the CPU -- and that's clearly low [I haven't factored where the operands
contents go]).  So I think CPUs will be capable of moving gigabits around.

Craig