Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!know!samsung!munnari.oz.au!metro!cluster!ultima!eric
From: eric@ultima.socs.uts.edu.au (Eric Lindsay)
Newsgroups: comp.periphs.scsi
Subject: Re: Adaptec ACB4000 & ACB5500
Message-ID: <18319@ultima.socs.uts.edu.au>
Date: 10 Sep 90 23:31:17 GMT
References: <177@lysator.liu.se>
Distribution: comp
Organization: SOCS, University of Technology, Sydney, Australia
Lines: 18

Adaptec jumpers (according to the manual, which I bought from 
Computer Surplus Store in California - they advertise regularly in 
Computer Shopper) are as follows.  Installed means bit = 1 or enabled.
Jumper Position   4000                   5500
A-B         LSB of SCSI address          SCSI reset option
C-D         SCSI address                 Reserved
E-F         MSB of address               Hard sectored LUN0
G-H         DMA rate (sysclock/4)        Hard sectored LUN1
i-J         Extended command set         Reserved
K-L         Not used                     Diagnostic mode
M-N         Syquest 312 support          Parity enable
O-P        Self diagnostics             SCSI address 2^2
R-PU        Write Precom off             SCSI 2^1
R-S*        Write Precom same as Reduced SCSI 2^0
R-T*        Write Precom all tracks   
The write precom stuff is in the ACB-4000A not in the RLL 4070.
Hope this helps.  Eric Lindsay, homebrew 68xxx forever!
eric@zen.maths.uts.edu.au