riscy
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Re: Should we have SCSI?

To: riscy@pyramid.com
Subject: Re: Should we have SCSI?
From: aki@akix.cts.com (Aki Atoji)
Date: Tue, 6 Jul 93 18:57 PDT
In-reply-to: <9307062116.AA10815@ubitrex.mb.ca>
References: <9307062116.AA10815@ubitrex.mb.ca>
Reply-to: riscy@pyramid.com
Sender: riscy-request@pyramid.com

   >     I would tend towards the 5380 type, as they are multiple sourced
   >     (cheap), well-known (Seagate ST-01), and can provide reasonable
   >     performance.  
   > 
   > Nope.
   > 
   > I wrote the Linux Seagate ST-01 (ie, with the Nat. Semi part) driver, and 
   > I would avoid this part like the plague.  ...

I've programmed 5380 in embedded SCSI arena as well.  I concur with
avoiding the chip.  The problem with this chip is that it's not much
more than a SCSI 'latch', and that this chip requires a lot of hand
holding by the driver code which tends to be a lot of work.  The
driver must step through each of the command phases, pretty much
monitoring the SCSI bus directly through the chip.  While this is an
excellent way to learn the actual SCSI bus operation (you start to
memorize waveforms this way), it takes a lot of code and uses up CPU
time.

The 53C9x series are definitely not this way and is recommended.  I
believe one of the PD OS's (BSD Net-2 tape?  Mach?) even had driver
for 53C94 in it.

---------------------------------------------------------------------------
Aki Atoji              Unix, X, Networking and Embedded Realtime Consulting
           aki@akix.cts.com                   crash!akix!aki@trout.nosc.mil
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