Hello Adam,
> Also, I think I've found some errors/ omissions in Kevin Horton's
> "sizes.txt" bank switching document. For example, $1FF8 and $1FF9 do
> not seem to be the only hot spots on F8 carts; $1FF7 also seems to be
> active (and many others). I don't think the hardware looks at the whole
> address bus to switch banks. Where is the CommaVid documentation?
> Ditto for the DPC, although I think there's enough info in the patent
> if I dig through all the patentese.
In F8 bankswitching only $1FF8 and $1FF9 are supposed to be
hotspots. But for some carts the timing is a bit sensitive.
On my 7800 based cartridge reader there were some F8 carts
that would switch banks at random addresses when the reader
was running at 7800 speed. I had to write a special routine
to operate at 2600 speed to be able to read out these carts
correctly.
The documentation for CommaVid's extra RAM format is in the
newest version of Kevin Horton's text. The games basically
have 2K of ROM at $1800-$1FFF and 1K of RAM at $1000-$17FF.
The RAM can be read from $1000-$13FF and written to at
$1400-$17FF.
The only format description that is still incorrect in Kevin's
text is Activision's FE bankswitching, which has been discussed
on this list some weeks ago. Have a look at the archive, if you
don't have these mails anymore.
I think the Megaboy bankswitching is still missing too. For this
one you just trigger address $1FF0 to switch to the next 4K bank.
The cartridge has 64K, so there are 16 banks.
The DPC patent covers everything you need to know about the
working of this cart. Basically it uses standard F8 bankswitching.
But there are 2K or extra ROM and a 255 byte random number sequence,
that you need to read out through the 128 R/W ports that the DPC
provides. You could have a look at the source code of the PC program
for my 7800 based cartridge reader for the exact sequence or which
addresses to write and read, if you can't figure it out on your own.
Ciao, Eckhard Stolberg
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