Author: root42

Here is another C64! This time around it’s one of the later C64C, also called the C64-II. It sports a look similar to the C128 and the Amiga, and on the inside it’s also a bit different to my Breadbin C64s. This particular model is pretty dirty, and I hope that it comes with a short board, sporting the SID 8580, because I do not have one of those. And of course I hope that it actually works, because I got it untested! So let’s open it up, clean it and make it shine like when it came out of the factory!

In this episode of our tour through the 8086 assembly language, we learn a few new opcodes and concepts CBW makes an appearance, as does the powerful XLAT for looking up values in … look-up tables! We use this to make a text mode plasma like effect. It is a bit simpler compared to what we did in another episode on the VGA card, but this time the executable is tiny, coming in at less than 170 bytes. We talk a bit about how to access screen memory in text mode and how to query the real time clock in the PC.

There are many diagnostic cartridges for the C64 which can help troubleshoot problems with broken or dead C64s. This new cartridge comes with three special features: it measures the 5V rail, which can cause problems with the machine, it shows the CPU clock, which can be the cause for black screens, if absent, and it can run three different diagnostic ROMs. The C64 Deadtest, C64 Diag and C128 Diag are selectable via a small switch. Let’s assemble this new troubleshooting tool and test it out!

Remember the clicking sounds of spinning hard disks? One “problem” with retro computing is that we replace those disks with Compact Flash, SD Cards or even SSDs. Those do not make any noises that you can hear under usual circumstances. Which is partly nice, because the computer becomes quieter, but also irritating because sometimes you can’t tell if the computer has crashed or is still working. This little device fixes that issue! It’s called the HDD clicker and it’s a very unique and funny little gadget!

In this video I will show you how to assemble your own SEGA MegaDrive/Genesis cartridge, using an erasable programmable ROM chip, a so called EPROM. Those can be had for relatively small money, used on eBay, for example. You also need an adapter for the popular TL866II+ programmer, to be able to read and write EPROMs up to 32 Megabits (4 Megabyte) in size. This can be used to make your own repro cartridges of rare games, homebrew or demoscene productions.

A user from the DOSReloaded forum sent me his dead Roland MT-32, arguably one of the most sought after and iconic synthesizers for playing vintage DOS games. This item is said to be totally dead, no LCD display and no sound. So let’s have a look at what’s wrong and if we can fix it!

Marco Roth reverse engineered a broken M396F mainboard, powered by a 386SX CPU. This tiny Baby AT sized mainboard comes with six 16 bit ISA slots, four 30 pin SIMM sockets, a 40 MHz AMD branded 80386SX CPU and is a fancy purple color! Does it work? Let’s throw some soundcards and games at it and see how it behaves! Marco didn’t have a lot of cards to test with, so I offered to do it for him. Let’s see how it turned out!

I was asked by a viewer if the Roland SoundBrush that I showed in an earlier episode can also be used to record MIDI music from a PC. And yes of course, it can. With some caveats though! I connected the SoundBrush to my 486 PC and tried a few games. Lucasfilm games were running into buffer problems on the SoundBrush, but Sierra games were playing nicely. Let’s have a look and a listen how you can wire up the SoundBrush, format some floppies and record some MIDI files!

In this episode we learn how to program a little tic-tac-toe game for two human players. No AI, just the input and output and the winning condition! We learn different methods to compare registers and memory locations, different conditional jumps and how to save a few bytes by replacing CALL instructions with JMP.

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!