 
 
 
                   ** Peterson XE Upgrade Errata ** 
              (Getting the ANTIC to see your extra ram.) 
 
                            E.Bachman 1990. 
 
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                   ** 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 
                    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. 
 