Commodore CASSIOPEI, User Manual

Page: 35 / 76

Now this has nothing to do with the Cassiopei, it was a problem ever since the VIC-20 came out
and the only way to solve it is to load these kind of games/programs to the intended loading address
as specified in the file. Therefore the Cassiopei menu shows this information, so you can get an
idea of the game/program will load or not before you select it in your current VIC-20 memory
configuration.
8.1.1 What to do when a VIC-20 program does not run?
Make sure that you are using the right memory configuration. It might be possible that you are
trying to load a file larger then the memory of your VIC-20, in that case add some additional
memory. But it may also be the case that the program you want to load might be a simple machine
language program with a BASIC stub. In those cases it is best to remove/disable the memory
expansion and load the file only when the BASIC start address matches the start address of the file.
Some memory expansion do not allow you to disable the 3K expansion that causes the BASIC start
address to appear at $0401, in order to disable that expansion (instead or removing the cartridge) a
simple set of pokes is enough to achieve this: POKE642,16:POKE644,30:SYS64818
A problem with loading files are most likely to be caused by an incorrect setup of the system. A file
that is too large to fit into the VIC-20's memory (because the file needs to be loaded on an
expanded VIC-20 instead of an unexpanded one), then it cannot work. In case of doubt use an
emulator with the same settings as your own VIC-20 in order to test if a program is capable of
running on your current VIC-20 memory configuration (see the next page).
The VIC-20 has so many different configurations that it is a little confusing. Below an overview of
different memory configurations and how they look like. The only directly visible difference is the
available memory for BASIC. But what you can't see is that the BASIC start address and the video
(screen and color) memory locations. Using the slow kernal loader, BASIC programs can be easily
relocated. But machine language programs require some trickery to make it work. But a clever
programmer can do this using his own relocation routines. An example is shown further on in this
manual. Be aware of the changing Screen memory locations, this may also cause a relocated
program to fail.
2019-10-27 Page 35 of 76 CASSIOPEI v2.0