Xref: utzoo comp.unix.i386:558 comp.unix.xenix:7764
Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!nuchat!steve
From: steve@nuchat.UUCP (Steve Nuchia)
Newsgroups: comp.unix.i386,comp.unix.xenix
Subject: Re: Mylex SCSI Controller
Message-ID: <14944@nuchat.UUCP>
Date: 24 Sep 89 22:07:30 GMT
References: <111006@nstar.UUCP> <653@fiver.UUCP>
Reply-To: steve@nuchat.UUCP (Steve Nuchia)
Organization: Houston Public Access
Lines: 24

In article <653@fiver.UUCP> palowoda@fiver.UUCP (Bob Palowoda) writes:
>From article <111006@nstar.UUCP>, by larry@nstar.UUCP (Larry Snyder):
>> Does ESIX directly support the 16550A in their ASY drivers?  I wish
>> that SCO did.

>Actually the problems are nothing but setting up the correct 
>conditions.

No, there is more to it than turning on the FIFO's.  A driver that
was written without considering a FIFO will in general not try to
do enough work on each interrupt.  To take full advantage of the
550A's fifo you have to make different tradeoffs than you do for
8250's.

In particular, if you know you are likely to be working with 4-16
characters at a time you spend a lot more code setting up pointers
and such than you will if you expect 1, sometimes 2 characters.  Some
drivers will even return from the interrupt service routines before
completely filling/emptying the queues.

-- 
Steve Nuchia	      South Coast Computing Services
uunet!nuchat!steve    POB 890952  Houston, Texas  77289
(713) 964 2462	      Consultation & Systems, Support for PD Software.