VIC-20 Cartridge combinations

Hi

I'm thinking about making a home made multi cartridge for VIC 20. (Yes,
I know that there are quite a few already but making the hardware is a
hobby for me).

For games it seems rather simple. Some are 4k at A000, some are 8k at
A000, some are bigger with 8k at A000 and more at either 2000 or 6000.
And there's the Scott Adams adventure games at 6000 too. Even though
there are different combinations, no single game cart requires or can
even make any use of any other cartridge (except perhaps in theory
40/80 column cartridges together with an adventure game). So here it's
just a case of mapping one set of rom images to the correct BLK outputs.

But for all other kinds of cartridges there are multiple possible
configurations. The most obvious is to have switchable ram at all
possible places (including the two I/O blocks) in the memory map.

But then there is all kinds of ROM cartridges that might actually be
useful to combine. For example Super Expander (the ROM part),
Programmer's Aid, VIC-MON, Basic 4.0, firmware for different hardware
(IEEE, 40/80 column cards) e.t.c.

(And VIC-MON comes in different varieties for usage at different places
in memory, although AFAIK it's only the 6000 version that were
officially sold, all others are relocations of that).

Also there are more than one monitor to choose from (VIC-MON, HES-MON
and maybe a few others).

Which combinations is of any use?

I'm thinking about a design whith four software writable registers for
freely selecting rom images for 6000, 7000, A000, B000 and some
hardware to reuse one of the registers for 2000 (for games) and perhaps
also reuse one of the registers for 4000 (for a relocated monitor).

Or should I go all the way with registers for each 4k block
2/3/4/5/6/7/A/B000 and for each 1k I/O block?

Combined with on/off for ROM and RAM for each 4k block would probably
make it possible to have any desireable configuration.

I already have a few EPROM:s large enough to contain most images that I
might want, and I also have a few 62256 32k SRAM chips, and some 6264
8k SRAM chips. I also have a few 28256 EEPROM:s, so maybe I'll add both
eprom and eeprom to be able to have the already known images in eprom
and homebrew stuff in eeprom.

Or am I just feature creeping it so it might never be buildt? Perhaps I
should go for a few dip switches to enable/disable rom/ram for each BLK
and use one EPROM for all stand-alone 4k A000 cartridges (i.e. mostly
games) and one EPROM for everything else with combined images
containing Super Expander, Programmers Aid, VIC-MON e.t.c.?

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