Here you will find a rough collection of tidbits for the C64.
A tool to back up data using a video capture card is described here.
A sample program that illustrates how to synchronize the CPU to the VIC-II raster counter. [ view ]
The following software all uses the above trick to illustrate some interesting and hidden features of the VIC-II chip.
The VIC-II has some kind of internal buffer to store each row of 40 text characters plus colour data. Each column in the buffer is 12 bits wide. The buffer is populated during 40 cycles every 8 scanlines while the screen is active. Because the VIC-II takes over the data bus while this happens these lines are also known as 'bad lines.' It is well known that you can trick the VIC-II into the 'bad line' mode at arbitrary moments by careful fiddling of register 17. There appears to be some magic method by which the 40x12 buffer is populated. To illustrate this I have created a small demo program. [ view source | download ] The VICE emulator gets this all wrong. See these screenshots.
Another nice C64 program. This one opens up the side borders. The nice thing about this version is that the number of active sprites does not affect the display. The object file is here. Some screenshots.
Note: earlier versions of the VICE emulator would display erroneous border patterns in the sprite demo. Apparently this is now fixed.
Originally written: 17 Apr 2005
Updated: 4 Apr 2017