root42

I have a couple of broken 1541 floppy drives for the C64 and similar machines. Some have broken mechanisms, of Mitsumi variety, where the read coils are fried, but also one drive that has supposedly some PCB issues. Let’s see if we can assemble a Frankenstein 1541 drive by taking bits and pieces from each drive!

In this episode we learn how to declare variables in assembly language. Also we learn how to access data from pointers stored in registers. We learn a couple of jump instructions and how to loop. We use this knowledge to compute all prime numbers below 1000 and print them to the screen. As usual this is based on the book “Programming Boot Sector Games” by Oscar Toledo.

Last time we restored Ocarina of Time to its former glory, this time it’s Majora’s Mask. This N64 cartridge was hit by last year’s flood, which besides hurting lots of people also claimed the less important artifacts, such as retro game collections. Here we have one example of a cartridge that was salvaged by the owner, before he sold it to me, untested. Let’s see if we can clean it up and get it going!

In this episode we learn how to use the DIV opcode for dividing integer numbers, how to print integer numbers to the screen, as well as how to use a debugger to understand what our program does. In all coding tasks looking for errors and understanding what the program actually does is a key aspect. So a debugger (here we use the Turbo Debugger by Borland) is a very useful tool that every developer should know how to use.

So you always wanted a Roland MT-32. Even as a kid you saw it in ads, and in the setup programs of games. But it was way to expensive. And today you still will pay upwards of 250 EUR for a working device, which is more than 30 years old. So why not emulate it? There is now a Waveblaster compatible module that will fit on many retro sound cards and which is able to emulate the MT-32 as well as SoundFont based GM and GS compatible synthesizers.

The SEGA GameGear that we revived in the last video gets a new shell! The old one was beaten up pretty roughly. And new shells in all kinds of colours are still made to this day. At the same time I will be replacing the electrolytic caps with small SMD ones. I disliked how the electrolytics were all over the place, making the shell hard to close. However something went wrong in the end, due to my own negligence…

I have had this SEGA GameGear lying around for a couple of years. I got it very cheap, because it was sold as broken, for parts. It came with a few games and the TV Tuner. Upon trying it out I noticed the power comes on, but all else seems dead. The GameGear is prone to have very bad capacitors, so that is the first order of the day: recapping! This and a modern LCD replacement are what we are going to tackle in this episode!

This is part three of our x86 assembly series. In this episode we learn how to do simple single character keyboard input. We use this to code a little game “Guess the number”. 

The Commodore DM602 is a small 10″ monochrome CRT, which pairs nicely with the VIC20 or C64. It has a built in speaker and a nice, very bright and sharp picture tube. This particular screen has a tiny problem, namely the video input socket broke off the PCB, so we will have to repair that. Also we will compare using different video cables on the C64, composite and YC (Luma/Chroma). This has some interesting visual side effects on the CRT.

For this year’s Christmas Episode of Let’s Code MS DOS we are revisiting Power BASIC and will be coding a very seasonal snowflake. It will be based on the Koch curve, especially implemented using an L-system. This is a rather easy system to describe fractal structures. It is not as hard as it might seem and you will be able to adjust the curve to display different things.