Newsgroups: comp.sys.ibm.pc.hardware
Path: utzoo!utgpu!watserv1!ssingh
From: ssingh@watserv1.waterloo.edu (The Sanj-Machine aka Ice)
Subject: Re: Adaptec AHA1542B max bus speed
Message-ID: <1991Jan13.031724.28829@watserv1.waterloo.edu>
Followup-To: comp.periphs.scsi, comp.sys.ibm.pc.hardware 
Organization: University of Waterloo
References: <1103@applix.com> <284500010@adaptx1>
Date: Sun, 13 Jan 91 03:17:24 GMT
Lines: 43

In article <284500010@adaptx1> neese@adaptx1.UUCP writes:
>
>There is also no jumper on the adapter for this speed setting, but can be
>done via software.
>
>			Roy Neese

From:
		aha-1540B/1542B user's manual rev 0.3 Dec. 1989

3.3.1.7 DMA Transfer Speed Default

Pin-pairs 12 and 13 of jumper block J5 set the default DMA transfer speed.
[stuff skipped] This speed may also be tuned to allow for the fastest
possible transfer (minimum bus on time) for any particular system by
using the Host Adapter command Set Transfer Speed. The Host Adapter
command overrides the jumper settings.

		Pin Pair		DMA Speed
		12  13			
============================================================

		 0   0			5.0 MB/s
		 x   0                 	5.7	
		 0   x			6.7
		 x   x			8.0

5.0 MB/s is the default. I was able to get the adapter and Seagate ST 296N
drive working at the next speed up.

Another version of the documentation I have for the 1540A/1542A has
speeds of 5.0, 6.7, 8.0, 10, and then 5.7. This is section 5.1.1.10.

These inconsistencies are irritating. But Adaptec is widely supported
so I guess they must be doing something right.

Ice.

-- 
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