Xref: utzoo comp.unix.xenix:3567 comp.unix.questions:9618 comp.unix.microport:1759 comp.sys.ibm.pc:20070
Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!uwmcsd1!marque!uunet!pilchuck!ssc!fyl
From: fyl@ssc.UUCP (Phil Hughes)
Newsgroups: comp.unix.xenix,comp.unix.questions,comp.unix.microport,comp.sys.ibm.pc
Subject: Re: *nix performance
Message-ID: <1488@ssc.UUCP>
Date: 6 Oct 88 18:29:56 GMT
References: <9902@ico.ISC.COM> <736@starfish.Convergent.COM> <1901@van-bc.UUCP> <4032@tekgvs.GVS.TEK.COM>
Distribution: na
Organization: Slugland, USA
Lines: 23

In article <4032@tekgvs.GVS.TEK.COM>, keithe@tekgvs.GVS.TEK.COM (Keith Ericson) writes:
> In article <2733@ima.ima.isc.com> johnl@ima.UUCP (John R. Levine) writes:

> >On machines with a PC AT bus DMA is rarely a win. It takes so long to get and
> >release the bus that it's faster to...

> We use Micom-Interlan NI5010 network interface boards around here.
> Their instructions indicate NOT to use DMA on an AT-class machine
> because a tight loop doing the data transfers is faster than the
> AT's DMA...

I can't argue with this but personally I like to think I could use
the CPU to do something other than bus reads and writes (even though
some consider this about the limit for an intel chip :-) ).

I have worked on fast mainframes.  Yes, the CPU can do things fast but DMA
I/O was used to free up the CPU.

Anyway, is DMA just slower when I have an idle CPU to do the transfer or
is there something magic that makes the CPU useless while DMA is running?
-- 
Phil Hughes, SSC, Inc. P.O. Box 55549, Seattle, WA 98155  (206)FOR-UNIX
    uw-beaver!tikal!ssc!fyl or uunet!pilchuck!ssc!fyl or attmail!ssc!fyl