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Article #215 (419 is last):
Newsgroups: freenet.sci.comp.atari.questions
From: aj421@cleveland.Freenet.Edu (Mike Rossman)
Subject: Basic XL/ST SS Drive
Date: Sat Jan 19 14:50:05 1991

Okay first of for question one I just got a copy of basic XL from my uncle. (You might know him, Top Cat[Ed Spisak]) okay.. so ann
on the extra commands that it allows.

Now for the ST Right now I have 2 Single Sided  standard atari ST drives yet it appears that Atari refuses to give the pinouts ou.
But anyway I was wondering if anyone out the could give me the pinouts to the Single Sided. Any help would be appreciated. Thanks.

Life It Seems to Fade Away. 
Drifting Futher Everyday
Getting Lost Within Myself
Nothing Matter No One Else.

Answered by Peter Haller 1/19/91

First sorry that this took so long....

I can't help you with the Basic XL questions. I suggest you ICD since they
now market (?) the Basic XL cart, along with the other OSS software.

To the drive question....

Basically all 3.5 drive are industry standard.  Atari, in their infinite
wisdom, chose to cut off one of the ST's arms by using single sided drives.
The pin outs for both single and double sided drives are the same. (I must
first say that I asume that the pin out you refered to is the 34 pin IDC male
connector on the drive itself.) The pinout is as follows:

PIN     description             PIN     Description
  1       GND                    2        NC or Density for 1.44meg drives
  3       GND                    4        NC
  5       GND                    6        DRIVE select 3
  7       GND                    8        INDEX
  9       GND                   10        DRIVE select 0
 11       GND                   12        DRIVE select 1
 13       GND                   14        DRIVE select 2
 15       GND                   16        Motor on
 17       GND                   18        Direction
 19       GND                   20        STEP
 21       GND                   22        WRITE DATA
 23       GND                   24        WRITE GATE
 25       GND                   26        TRACK 00
 27       GND                   28        Write Protect
 29       GND                   30        READ DATA
 31       GND                   32        HEAD SELECT
 33       GND                   34        DISK CHANGE

Well there you have it.  The only difference between single and double
sided mechanisms is that pin 32 - Head Select- on the single sided
drive doesn't, or rather can't do anything, other than give you an error.

In terms of upgrading to double sided mechs, I have done this and can 
tell you that ANY IBM compatible drive will work.  I used Mitsumi (?)
drives from Compuadd and they worked fine.  One WARNING:!!!

Make sure you check the power connection to the replacement drive.
Some of the older drives that Atari - Chinon drives - required both
+5 and +12 volts. It seems that many of the ST mother boards supply both
voltages regardless of the drive used.  This causes no problems with newer
drive that only need +5, most only need +5. BUT, when connecting the
power connector to the new mech MAKE SURE THAT +5 from the ST goes to +5
on the drive.  If you connect the +12 line to the +5 drive line - goodnight
drive.  YOU WILL BLOW the read/write head on the drive - I know I did
this on a drive that had the power connector reversed on the drive.
Most drives label the pins for the power, but make sure!

One other note: The alien drive will most likely not fit very well into the
atari boxes.  On STfm's a little cutting works, on extern SF354's , well
plan on spending sometime figuring it out.  For one thing the ribbon cable
in the atari's are upside down and VERY short.  On the cable:  If it doesn't
work one way - try it the other - no harm can be done by reversing this
cable ,as with the power cable.  

JUst remember, when ever you mess with the hardware


                                Peter Haller


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