Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!sci34hub!cdthq!gary
From: gary@cdthq.UUCP (Gary Heston)
Newsgroups: comp.os.cpm
Subject: re: Using 3.5" floppies instead of 8" floppies
Message-ID: <kgJaX1w161w@cdthq.UUCP>
Date: 13 Feb 91 04:53:55 GMT
References: <1991Feb11.092925.46847@cc.usu.edu>
Organization: Garys' Home for Obselete Computers
Lines: 20

slsw2@cc.usu.edu writes:
> 3.5" drives use CMOS drivers for the signals that they drive, and therefore
> cannot drive the terminators generally used for 5.25" and 8" drives. The
> data sheets for the Intel 82077A therefore recommend that if you are going to
> mix 3.5" drives with 5.25" drives, you include a buffer between the 3.5" and
> 5.25" drives so that the drive doesn't have to try to drive the 5.25"
> terminator.

Shucks, pull out the terminator. If they're driving the circuit with
CMOS, you won't need it--they were designed originally for open-
collector drivers, which CMOS isn't. If all else fails, build a 
replacement terminator out of higher value resistors. 

It's been my experience that drives and controllers work fine even
when double terminated, both hard and floppy. We've never had a
problem at work (we build ISA systems) with weak signals from 3.5"
drives, and we intermix them constantly.

Gary Heston, at home.....
gary@cdthq.uucp