The VGA card can display up to 256 colors on the screen at the same time, using an indexed 8 bit color mode. This is not much, but it allows us to fade two 16 color images into each other. This looks pretty nifty!
Tag: retrocomputing
The OneROM Versatile ROM Emulator
The old home computers like the C64, PET and VIC20 use a lot of 24 pin ROM chips. Many of those are failing and are often replaced with EPROMs and adapter boards. Those are sometimes hard to acquire, especially for older machines such as the PET. But even more common EPROMs require a dedicated UV eraser, programmer like the Minipro, which all adds up. The OneROM is a versatile replacement for EPROMs based on the RP2350 MCU. It allows for easy reprogramming, multiple ROM images and can replace up to three ROM chips in a single system. Oh, and it’s open source!
Commodore 4040 Disk Drive Repair
We have another Commodore IEEE-488 dual disk drive. It is the predecessor of the 8050 and it is almost compatible with the 1541, the C64’s disk drive. This specimen doesn’t work, its drives look quite mangled. So let’s fix it! But it is never that easy…
Let’s Code MS DOS: 0x32 VGA Split Screen
A couple of games back in the 1990s utilised the VGA split screen functionality to enable things that were otherwise only possible on more capable machines, like the Amiga. The VGA split screen allowed games such as Jazz Jackrabbit or Pinball Fantasies to display a static status bar at the bottom of the screen, while the rest of the screen was smoothly scrolling in two or more directions. In this video I will show how this is possible, and which VGA registers to program with the appropriate values.
Commodore SFD 1001 Repair
Another dead floppy drive has landed on my desk. I was told that “the motor isn’t working”. That can have different causes, but let’s find out what the actual problem is. I never worked on one of these drives before, but they are related to the CBM 8050, a drive that I like very much.
Spin Me Round: Commodore 1541 Repair
We have another dead 1541 floppy disk drive on the bench today. It is an infinitely spinning drive, so it means that somehow the drive is not booting. But what might be the cause…?
Double Trouble: C64 and 1541 Repair
I have two dead Commodore devices here, that a user asked me to repair. A 1541 floppy disk drive and a bread bin C64. The drive’s motor spins indefinitely and the LEDs don’t come on. The C64 has a black screen. So let’s get cracking, and repair both! With the C64 I made a couple of wrong turns, but in the end all turned out well! The 1541 had some other idea in store for me, and turned out to be a bit on the spiritual side…
Pico DRAM Tester
Eric Schlaepfer aka TubeTime has released an open source tester for vintage DRAM ICs. It is based on the fabulous Raspberry Pi Pico 2 microcontroller. It supports even older chips that use -5V and +12V. I ordered PCBs and the components for building the tester, so let’s warm up the soldering iron and build something!
Let’s Code Commodore PET 0x02: Snakes on a PET
In this episode we code a simple game for the PET. It is the classic snake game, where you control a snake that picks up food and grows longer. We learn how to read from the keyboard, and how to limit the speed of the game, as the PET is slow, but not THAT slow.
Commodore C16 From Hell Repair
This is another dead Commodore machine from the pile of machines that eazy brought over at the beginning of the year. This time it is a TED machine: the venerable C16. It is completely dead, shows no signs of life. But this has never stopped us. Probably a dead CPU. How bad can it be, eh?