[abc80] Super Smartaid Cartridge

[H. Peter Anvin]

I remembered that address 0x7800 is where the PR: jump table lives --
apparently SSA takes the place of the printer ROM (30K), not, as I first
thought, the unused space at 0x7400 (29K).

That made it a bit easier to make educated guesses as to the bit
scrambling of SSA1; the sequence turns out to be 61250347.

I have put the descrambled and disassembled ROM files at:

https://www.abc80.org/docs/roms/ssa/

It also makes it obvious that there is not separate paging for SSA1 and
SSA2; they both use the same page bit.  The Magnum, which has a 16K
EPROM here instead of 2K, obviously has more paging bits, but one of the
pins on the new flip flop chip is pulled to A8 on the address decoder
chip -- the one that is totally unused on the Super -- so that implies
that in this version the paging bits also affects which EPROM is
selected (makes sense, since one probably doesn't want to page things in
and out of a tiny 1K window; it probably also has code in the large
EPROM for the larger 4K window, and maybe uses the 2K IEC area too.)

Fun stuff.

	-hpa