Classic Computer Magazine Archive COMPUTE! ISSUE 34 / MARCH 1983 / PAGE 12

VIC Expansion Memory

A problem has developed with my VIC-20 computer that I do not know how to solve.

I have found that the ads lead you to believe that the VIC is expandable, but one or more RAM cartridges installed will not run most of the programs I now have.

How does one overcome this problem? Can you put me in touch with someone who can help me? Thank you for your time.

Leon A. Weitzel

When you add RAM to a 5K machine, the VIC "adjusts" itself to the extra memory. The screen memory moves to a new location, the start of BASIC relocates, and a few other pointers move around.

You can determine where the screen memory (normally at 7680) resides on any size VIC:

SCR = 4 * (PEEK(36866) AND 128) +
64 * (PEEK(36869) AND 120)

If you use the above formula within your programs, they will run on any VIC, regardless of memory size.