2e7613d0   
   XPost: comp.sys.cbm   
   From: z80eu@arcor.de   
      
   hollowdrutt@gmail.com wrote:   
   > Perhaps it's possible to get one of the other cartridges with the same   
   > configuration and replace the rom, but they might have used some odd   
   > parts,   
   > or made other efforts to prevent manipulation so you might be better   
   > off building   
   > something yourself from scratch.   
   >   
   > I have built an Ocean cartridge just using the crt documentation   
   > and a tutorial on building your own 8KB cartridge and it worked fine,   
   > so I will happily assume the same method can be used for this one,   
   > until proved wrong ;)   
      
   Unfortunately it's not an "Ocean" one. And I am sure there are   
   differences between the cartridges of these vendors.   
      
   > The eprom and it's content is the easy part, use cbmcart to get a rom   
   > file,   
   > then burn it to a regular 64 KB eprom.   
   > The data is stored linear and 8KB is switched in at $8000 at a time   
   > using the   
   > address lines. You connect the lower address lines from the c64 to the   
   > lower   
   > address lines of the eprom, and use ROML from c64 as chip select.   
   > Since the cartridge uses bank switching by writing the bank number to   
   > $DE00   
   > you need a buffer circuit using /I/O1 of the c64 as chip select with   
   > the data lines of   
   > the c64 as input and the high adress lines of the eprom as output.   
   >   
   > For this cartridge you will also need to store values for the EXROM   
   > and   
   > GAME lines on the c64, based on values written to $DE00. The   
   > description   
   > in the crt documentation looks like it is enough to figure out what   
   > logic to use   
   > but I would also double check with the part about memory   
   > configuration   
   > in c64 programmers reference guide.   
      
   I have a spare "Magic Desk" cartridge, but it's only a 32kB cartridge.   
   Do you know any other 64KB cartridge which is similar an addressing and   
   memory schema ? If so, may be I will look for that one and buy it, then   
   replace the ROMs with the Vindicators content EPROMs.   
   I have seen also at http://markus.brenner.de/cartridge/index.html a good   
   explanation of the cartridge structure, but I need still a kind of   
   "carrier" for the 64KB ... may be there is also a blank EPROM module   
   available for four or eight (?) EPROMs, but at the moment I own only a 2   
   socket blank EPROM module carrier, so I am sure 2x 32KB EPROM without   
   bank switching logic at the $DE00 address with for sure NOT work.   
      
   Regards   
     Peter   
      
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