Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!mailrus!ames!vsi1!octopus!pete
From: pete@Octopus.COM (Pete Holzmann)
Newsgroups: comp.periphs.scsi
Subject: Trouble in SCSI-Land: On PC-computers, it isn't really standard!
Message-ID: <1990Mar15.042028.16024@Octopus.COM>
Date: 15 Mar 90 04:20:28 GMT
Reply-To: pete@octopus.COM (Pete Holzmann)
Organization: Octopus Enterprises, Cupertino CA
Lines: 45

Based on experiences during the past 6 months, I've come to the sorry 
conclusion that SCSI is not defined well enough as an interface standard,
at least in the PC world. [If SCSI is the base I/O scheme for peripherals,
as in the Mac, etc, then I'm sure things ought to be much better...]

I'd love to be proven wrong; I'd love for someone to tell me 'there will be
a good solution in N months'. Does anyone have any insight?

First: no complaints about the interface between SCSI controllers and SCSI
devices. That works, and works well. 

Unfortunately, that isn't enough! There are 2 major problems:

1) There is no standard way for software to talk to a SCSI controller
2) There is no standard way for a DMA-based SCSI controller to deal with
    the '386 or '486 CPU's, which make a habit of changing memory maps
    on the fly.

Some pretty awful problems result:

From problem 1: Buy 4 SCSI peripherals. Likely as not, they will come with
    some custom interface software (drivers, etc.), and 4 different SCSI
    interface boards. All (or mostly) mutually incompatible. This is MUCH
    worse than normal custom interface cards. The SCSI cards all think they
    are 'standard', and end up interfering with other SCSI cards in the 
    system! Specific example: SCSI hard drive, SCSI 9 track tape, SCSI
    magneto-optical drive, SCSI Worm drive. Can't make them play together!!!
    Sick.

From problem 2: I know of no SCSI controller on the market that functions
    completely correctly with multitaskers, RAM organizers, Disk Cachers,
    and the like. I suppose a completely dumb one (polled I/O) might, but
    then you lose the performance gain of DMA. Isn't there anybody out
    there who's done a DMA-interface SCSI disk device driver that works
    in these kinds of situations?

Feeling somewhat disgruntled by the whole mess...

Pete
-- 
Peter Holzmann, Octopus Enterprises   |(if you're a techie Christian & are
19611 La Mar Ct., Cupertino, CA 95014 |interested in helping w/ the Great
UUCP: {hpda,pyramid}!octopus!pete     |Commission, email dsa-contact@octopus)
DSA office ans mach=408/996-7746;Work (SLP) voice=408/985-7400,FAX=408/985-0859