Path: utzoo!attcan!utgpu!watmath!clyde!att!occrsh!occrsh.ATT.COM!rct
From: rct@occrsh.ATT.COM
Newsgroups: comp.sys.att
Subject: Re: Hanging a 2nd disk off a 3b2-310?
Message-ID: <144800033@occrsh.ATT.COM>
Date: 10 Jan 89 20:30:00 GMT
References: <7057@batcomputer.tn.cornell.edu>
Lines: 42
Nf-ID: #R:batcomputer.tn.cornell.edu:-705700:occrsh.ATT.COM:144800033:000:1339
Nf-From: occrsh.ATT.COM!rct    Jan 10 14:30:00 1989


Peter Fales mentioned a quick hardware hack to allow old 3B2/300 motherboards
(CM-190A, artmaster 5 and older) to handle up to 16 heads/drive.  The "white
wire" should be run from pin 27 of the NEC7261 to pin 3 of the LS14, rather
than to pin 12 of the LS14 (third pin on the left, rather than the third pin
on the right).  Here is a corrected sketch of the modification that I cribbed
from Peter's article:


I NOR AT&T CAN TAKE ANY RESPONSIBILITY FOR ANY DAMAGE TO YOUR SYSTEM
AS A RESULT OF ATTEMPTING THIS MODIFICATION.


My notes don't indicate what this chip 
is (LS14 as mentioned earlier -- ed.),
but it is right next to the Hard
Disk controller chip in this physical
location.
	|
	|
	v
 +-----------------------------+
 |  --------- 	-------------  |
 |  |       |	|	    |  |
 +--|3      |   |	    |  |   <--- NEC Hard Disk Controller Chip
    |       |   |           |  |	1) Isolate Pin 23
    |       |   |	    |  |	2) Add Wire from pin 27 to pin 3
    |       |   |	    |  |
    |       |   |	    |  |
    ---------   |	    |  |
	        |	    |  |
	        |	    |  |
	        |	  27|--+
	        | 	    | 
	        |	  23|--X
	        |	    |
	        -------------

Enjoy!  I tried it out on an old AM5 motherboard and it DOES work!

--Bob Tracy	AT&T Network & Data Systems	Oklahoma City Works
att!occrsh!rct	(405) 491-4577