Convert Vic20 8k cart to jumperless multi 16k cart

[kevgal]

Gday guys , this may have been mentioned in the past but a jumperless 16k mega cart can be made from an old 8 k cart with just 6 diodes and 2 resistors (and extra resistors for the thumb switches).
works for all 16k variants that use memory blocks 5/3, 5/1, 2/3.
You just need a cart with the intact edge connector pins for blocks 5,3,2 and 1 which the Japan made ones seem to have.
Even works with Baldors Gate (just need to swap the upper and lower 8k blocks around).
Works okay with 1N4148 diodes but would probably be better to use an alternative with a lower forward bias.

[chysn]

What do the thumb switches do?

[Vic20-Ian]

Guessing it is a flash cart with manual address to pick an image.

[Mike]

What do the thumb switches do?

They select one of 64 possible cartridge images.

Guessing it is a flash cart with manual address to pick an image.

The M27C801 is an EPROM, not Flash. You need an UV lamp to erase it and an EPROM programmer to write new contents.

[kevgal]

Some more circuits.
The 16k/8k version requires internal ram and makes the most of BCD thumb switches.
The 4k version doesn't require internal memory expansion.

[Mike]

kevgal,

no disrespect intended, but your designation of the cartridge mods as being 'jumperless' is a misnomer. You use BCD thumb switches to do a selection on the upper address lines of the EPROM. While it might be slightly more comfortable than setting/removing jumper pins or using DIP switches, all these are mechanical solutions. A true jumperless solution would involve a latch to hold the upper address lines and a menu firmware to set that latch on user input.

The 16k/8k version requires internal ram and makes the most of BCD thumb switches. The 4k version doesn't require internal memory expansion.

What kind of internal RAM expansion are you talking about?

Greetings,

Michael

[kevgal]

Gday Mike, by jumperless I meant that there was no need for jumpers between the memory blocks that some dev carts use. The mod to a cart that has all block select pins present means that the memory blocks at block 5 and 3 also appear at blocks 2 and 1 which means all carts that use various memory blocks all work without having to 'jumper' their correct memory blocks.
I have converted most Vic 20 games that are 16k or less to cart format. These auto start at $A000 and copy themselves to ram then run the program. The 4k or less carts all work with the standard ram but the larger games require expansion ram which I have installed internally.
Cheers
Kev

[Mike]

[...] the memory blocks at block 5 and 3 also appear at blocks 2 and 1 which means all carts that use various memory blocks all work without having to 'jumper' their correct memory blocks.

This mirroring trick depends on the observation, that most CBM cartridges with two ROM sockets had their jumper pads arranged so one of the ROMs could go to either BLK1 or BLK3 and the other one to either BLK2 or BLK5. This allows for four different combinations, two of them span 16K in BLK1/BLK2 or in BLK2/BLK3. The two combinations BLK1 with BLK3 or BLK2 with BLK5 are disallowed.

Eslapion's Behr-Bonz cartridge uses exactly the same mirroring method and could be cited as prior art.

I have converted most Vic 20 games that are 16k or less to cart format. These auto start at $A000 and copy themselves to ram then run the program. The 4k or less carts all work with the standard ram but the larger games require expansion ram which I have installed internally.

This still does not answer my question what kind of internal expansion in your VIC-20 exactly is. If anything, mainboard mods are even less standard than your typical cartridge mod. How do you handle bus contention between internal memory and cartridge expansion, for example?

[doug_in_nc]

I have converted most Vic 20 games that are 16k or less to cart format. These auto start at $A000 and copy themselves to ram then run the program. The 4k or less carts all work with the standard ram but the larger games require expansion ram which I have installed internally.
Cheers
Kev

It would be great if you could post the cartridge images you have created somewhere. I'm sure that they would be of benefit to a lot of people. I for one, would love to have a cartridge version of Bonzo

[MCes]

Making a game cartridge from a game created for an expanded VIC20 is a desire that can be easily realized also with the jollycart,
the goal become great because into jollycart there is the ram expansion (+24k) too: no multi slot adapter or internal modify are required
viewtopic.php?f=11&t=10235#p114617

An example... Bonzo!
viewtopic.php?f=11&t=10235&start=15#p114672

[kevgal]

Here are all my 'cartified' programs.
The 0k carts don't need any expansion ram but the others do so a dev cart like Jolly Roger cart would be ideal.
Some of the files are homebrew so if anyone has any objection to their inclusion I shall remove them (or any others).
I've included the split 16k versions to use in emulators.
Cheers
Kev

[kevgal]

This still does not answer my question what kind of internal expansion in your VIC-20 exactly is. If anything, mainboard mods are even less standard than your typical cartridge mod. How do you handle bus contention between internal memory and cartridge expansion, for example?

Gday Mike when I use internal ram with the external multicart I only switch in the required ram for the programs to run (0, 3k, 8k or 16k).
I use a thumb switch to select ram.

[doug_in_nc]

Here are all my 'cartified' programs.
The 0k carts don't need any expansion ram but the others do so a dev cart like Jolly Roger cart would be ideal.
Some of the files are homebrew so if anyone has any objection to their inclusion I shall remove them (or any others).
I've included the split 16k versions to use in emulators.
Cheers
Kev

Thanks. Much appreciated!