Articles by John Linville

My project for RC2019/03 is to write a chip tune player for the Tandy Color Computer (CoCo) that utilizes the SN76489 chip on the Game Master Cartridge (GMC). This is not a tool for creation but a utility for consumption. So, what will it consume?

VGM Files
The VGM file format is …

It’s RetroChallenge time once again! In fact, we are already five days into the contest, and I still haven’t posted a “start” entry. I reckon it is time to fix that… 

Project Description 
I’m going to work on a Tandy Color Computer (CoCo) project that enables the use of the CoCo’s Game …

In the previous post, I explained the difference of intent between “logical” and “arithmetic” shift operations in assembly language. I also demonstrated that for two’s complement binary numbers, the bitwise effects of logical-shift-left and arithmetic-shift-left are actually identical. This makes the choice to implement a single physical instruction that covers …