Classic Computer Magazine Archive COMPUTE! ISSUE 32 / JANUARY 1983 / PAGE 10

VIC Custom Characters

I recently added 8K to my VIC-20. This causes new locations in RAM to be assigned to the start of BASIC, the screen area, and color control area.

There is a technique for using custom characters on the 5K VIC-20 that involves moving down the end of the BASIC RAM working area from page 30 to page 28 and loading pages 29 and 30 with the custom characters. Every custom character program that I've seen uses this technique – POKE 56,28:CLR.

Both the screen RAM and custom character area must be located below page 30 in RAM to work. Unfortunately, with the 8K expansion (and without 3K) there is no space available below page 30. The obvious thing to do is to relocate the start of BASIC text from page 18 to page 30, since with 8K the top of RAM is page 64. This appears possible by changing locations 44, 46, 48, and 50 from 18 to 30. Unfortunately, it doesn't work. The RUN command results in a Syntax Error and GO TO yields Syntax Error in statement 0. (LISTS do work though.)

This wordy prelude leads to my question: Is it possible to have custom characters (and alternate screens) with the 8K expansion (and without the 3K)? If yes, how?

Dick Gough

Several readers have inquired about this. Unfortunately, there is no known solution at this time. Several programmers are currently working on this problem and we'll publish the answer as soon as it is solved.