You can savely assume that a game which requires 8K will also run with a 16K or 24K expanded VIC-20. This is because the three main different things to the unexpanded VIC, namely the screen address (shifts from 7680 to 4096), the colour RAM (shifts from 38400 to 37888) and BASIC start (shifts from 4096 to 4608) all remain the same across the 3 different extensions. Only the top of BASIC RAM differs, but other than giving more RAM for the programs (obviously) all other POKEs and PEEKs remain the same. Incidentally, that also means a game designed for +16K will run on a +24K expanded VIC-20. Regarding user defined characters with +8K or more, that topic has been discussed in recent threads.OBSysteme wrote:What level of extra ram would I likely need, 3k 8k 16k etc.? [...] I like the idea of trying to fit it in 8k. 8k ram seems a common cart and from what I understand, higher ram configurations would probably be able to load it as well?
Two points to note:
- the biggest single memory expansion available from Commodore was the VIC-1111, +16K RAM. This is a 'soft' limit I'm setting myself, i.e. I do make myself at least *some* thoughts whether or not to straddle that boundary, because ...
- when confining oneself to 'original' CBM hardware at that time, one would have had to buy a cartridge extender, buy a +16K and +8K RAM extender, open the latter one to set it to BLK3, and insert both cartridges into the extender just to get +24K RAM. Obviously quite an expensive method.
...
Of course there are also third-party RAM cartridges around, even with more than +16K RAM. From the programmer's point of view, they are all equivalent.
Finally, three newer cartridges, namely Mega-Cart, FE3 and Ultimate Expander have found some good acceptance. These all allow to extend BASIC memory by +24K, and also allow for RAM in BLK5, which just unfortunately is not continuous with the other RAM extensions, thus can't be added to available BASIC RAM. Even if you write your game for +24K you can be sure that 200+ people around the world can run it on real hardware. All those who do not own such a RAM expansion still could run it in VICE - maybe even giving them some incentive to buy one of the aforementioned carts?
Greetings,
Michael