From: Michael Current (aa700@cleveland.Freenet.Edu)
Date: 10/30/94-03:23:44 AM Z

From: aa700@cleveland.Freenet.Edu (Michael Current)
Subject: percom
Date: Sun Oct 30 03:23:44 1994

From: dh395@cleveland.Freenet.Edu (Steven J Tucker)
Date: 18 Oct 1994 07:57:54 GMT

If anyone is interested, here is a letter I wrote to a guy on how I 
  convert my percom drives to higher capacitys.


>The model number is AT88-S1PD. It just has one drive in there.
>I can format it in single density just fine but that's about 
>it. There aren't any dip switches but there is a 34 pin connector
>and an edge card connector for a printer I think. Is it possible
>that this is only a single density drive? The drive mech. is
>a Tandon I think from the last time I opened it. I think you
>said something about getting a y-connector to handle 2 drives.
>Wouldn't that put a strain on that little power supply inside?
>Just wonderin'. Well, I stop blabbing now. Thanks for any help
>you can give me.

You have the Single Density version of the Percom drive.  But ALL percom drives
 support DOUBLE SIDED 80 TRACK OPERATION.  You can still hook up and 3.5"
 drive but you will only get 360k instead of 720k.  All Double Density
 models are serial numbered RFDXX-sY where XX is the number of tracks
 on the mech ORIGINALLY installs, and Y is the number of SIDES on the mech
 originally installed. 

My percom w/ 720k mechs is labeled RFD40-S1.  It originally contained a 
 FULL HEIGHT single sided 40 track drive.  A real beast to remove.

The Tandon Mech inside MAY be a single sided 40 track mech, which was top
 of the line at the time it was made, but the controller will support 80
 tracks DS.

The 'EDGE CONNECTOR' sticking out the back is a pass through connector to
 hook up more floppies.  To convert your drive to 3.5" mech do the following:

1: open the drive and REMOVE THE 5.25 mech and toss it in the trash ;)

2: REMOVE THE EDGE CONNECTOR BOARD and the cable that connects it to the
   main controller board, there may also be a single ground wire running 
   from the card to the controller/power supply.  Cut this ground wire and
   remove the edge connector board.  You can discard the edge connector board,
   you will never need it again.

3: Buy some 720k drives.  Dont bother with 1.44Meg drives, they will just be
    a waste of cash since you will only get 720k.  The Percom does not support
    the higher transfer rate used in 1.44m mode. (Since it didnt exist when
    the controller was made ;)

4: This is the tricky part.  You will notice the drive connector on the main
   board is the exact same type as on a regular IBM floppy drive board!
   If you just want 1 360k drive just go get a regular PC internal floppy
   drive cable for $1 and plug one end into the board and I end into the 
   720k drive.  If the cable you get has connectors for 2 floppies on it and
   a twist in the wire near the middle, DO NOT USE THE PORTION OF THE CABLE

   If you want more than 1 3.5" drive, get a STRAIGHT THROUGH cable that has
   no twist and more connectors. The Percom Controller wont work correctly 
   with PC type cables that contain the twisted wire pair.

   You can build your own pass-through cable from parts from Radio shack if
   need be, just get regular 34pin connectors and a ribbon cable.

5: Power supply considerations.  The 3.5" mech will need an adapter to 
    draw power from the large 4 pin connector on the Percom power supply, this
    is a STANDARD PC POWER ADAPTER and should come with your drive.  If it
    does not it costs $2 at radio shack.

   If you want to power more than 1 drive get a standard PC POWER SUPPLY 
    Y-splitter.  The power drain of 2 3.5" drives in my Percom is roughly
    only 2/3 of the draw of the single old FH drive.  No need to worry about
    toasting the power supply.  If you want more then 3 drives hooked upto the
    unit (it will support 4-8, depending on the 3.5" drive types) I would
    suggest you invest in a cheap PC power supply.

6: Drive selection.  Drive number selectionis handeled from the drive unit
    exclusivly on SD units, set the jumper on the 3.5" drive to D0 or
    'Drive A' or whatever is FIRST.

7: Once you get the drive powered and connected, its time to give it a 
    test.  Turn on the drive, carefull not to let anything metallic 
    come in contact with the main board.
   If all is correct you will hear the drive motor spin for about 2 seconds
    and the BUSY light on the front will flicker for 2-3 seconds and then
    go dark. 

   If you oriented one of the cable ends backwards (easy to do w/ a homebrew
     cable) the drive light will be lit forever when you turn on the drive
     and WILL NOT GO OFF. The motor may also spin forever.  This will NOT
     harm the drive or controller, just reverse one end of one of the cables
     and try again.

  Hook the drive to a computer and power on the drive, after the light goes 
   off turn on the computer.  If you hooked up the power supply, drive 
   cables and drive selector CORRECTLY the drive BUSY light should come
   on as the Atari tries to boot from it as normal.

  Turn both units off.

8: You now have a perfectly good 360k drive! ;)  Just get MyDos loaded, hook
   up the drive and use the configure option to set the drive controller
   to 2 sides, 80 tracks, SINGLE DENSITY.  the seek time should be set to   
   the fastest possible (0 if I recall).

   Its been awhile, but I think the options go: High Capacity: NO
                                                Configurable: YES
                                                Double Sided: Yes
                                                Tracks: 80
                                                Seek: (fastest)

9: Format a disk at this density, it takes quite awhile. Write DOS/DUP and
    you now have a bootable 360/720k disk!!!!  These drives are real 
    speed demons in SD too, you will love that!

These drives work fine w/ SpartaDos as well (no ultraspeed).

The only modification to the above directions for DD drives is that the RDF 
 drives have dip switch settings to control the 'drive offset'.  You can adjust
 these so that physical drive 1 is atari drive 5, etc.  these switches are
 not present on any of the SD drives I have owned.


-- Video game playing, adventure junkie, choclate craving, woman loving, 
    Limbaugh hating, Trek watching, all around lazy computer fart.

!! Request my *FOR SALE* LISTING OF CLASSIC VIDEO GAME STUFF !! 2000+ Lines !!
Michael Current, Keeper of the 8-Bit Atari FAQ & Vendor/Developer Lists
 Cleveland Free-Net Atari SIGOp: aa700 /

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