Peterson XE Upgrade Errata

From: Michael Current (aa700@cleveland.Freenet.Edu)
Date: 01/09/93-04:31:21 PM Z

From: aa700@cleveland.Freenet.Edu (Michael Current)
Subject: Peterson XE Upgrade Errata
Date: Sat Jan  9 16:31:21 1993

                   ** Peterson XE Upgrade Errata **
              (Getting the ANTIC to see your extra ram.)
                            E.Bachman 1990.
                   ** Should I be reading this?? **
       If you are using a stock 130XE or a Rambo'ed 800XL you have no
   need to read any further, (other than for informational purposes).
   Also, CSS modified XE's are built in accordance with the modification
   listed below. This text concerns you if you are using an XE of
   greater than 128k, OR (more specifically), if the Wedge's FORMAT
   command results in an apparent system crash.
       In the process of developing the current revision of the Wedge, I
   stumbled across an interesting bit of information. It seems that the
   320k Peterson XE upgrades don't allow for the ANTIC chip to access
   extended ram. Anyone familiar with this upgrade knows that the antic
   enable pin of the PIA chip gets lifted from the motherboard to
   provide for the extended addressing needed to access the extra ram.
   Thus leaving the ANTIC's extended bank addressing capability
   untapped. This can be overcome by tying the antic and cpu's enable
   lines together (much the same way as it's done in the rambo'ed XL's).
   Correcting this is simplicity itself, simply tie pins 14 and 15 of
   the socket for the PIA, together, (you know, that socket that you
   hopefully installed when you did your upgrade?), If not, simply run a
   short jumper from the pad on the motherboard that pin 15 used to
   occupy, to pin 14 on the same chip, (the PIA).
       NOTE: From the docs I've seen, the larger Peterson XE upgrades look
   as if they also neglect the antic enable line. This minor mod should
   work just as well on them as it has on the 320k XE's.
                  ** So what does this mean to me? **
       Well hopefully you're reading this before you've run the wedge
   and found out that the format command bombs out in a major way. Why?
   because the format command uses a custom screen and display list, run
   out of the extended ram. Thus ANTIC, being unable to access extended
   ram will attempt to generate a screen from whatever data is in the
   main bank at those particular locations. The resultant display will
   usually be a blank screen, or some unreadable garbage. To address
   this, I've included a specially written format program,
   "P_FORMAT.COM". In order to demonstrate the format function to those
   whose machines are unable to use the Wedge's internal format command.
   AND, to hopefully coerce you to perform this simple mod to your XE.
       I realize, it is not normally the place of the software developer
   to tell users, "well, just modify your machine to use my software".
   However I feel most strongly, that this feature will enhance the use
   of your expanded XE, as well as make it compatible with future
   programs that may use the extended antic access. As well as with the
   Wedge and future Wedge Disk Accessories.
       In closing I wish to thank Scott Peterson for his series of XE
   upgrades and in no way intend for this text to berate his fine work
   on the Atari 8-bit.
                           Ed Bachman  1-3-90.
         Michael Current, Cleveland Free-Net 8-bit Atari SIGOp
Carleton College, Northfield, MN, USA / UUCP: ...!umn-cs!ccnfld!currentm
      Internet: / Cleveland Free-Net: aa700

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