Here is a little refresher on how memory management and pointers work in the C programming language, and especially under real mode MS DOS programs written in Turbo C 2.0. We will go back to the basics to give all the new subscribers of this video series a chance to catch up.
Tag: retrocomputing
Let’s Code MS DOS 0x2A: Background Adlib Music
We already learned how to program the Adlib sound card to produce percussion and melodic instruments. Now we tackle the problem of getting real music out of it. By utilizing the Reality Adlib Tracker’s playback routine we learn how to program the Programmable Interrupt Timer (PIT) in the PC to get a steady playback of background music.
Zombie Floppy: How To Revive A Broken 1541 Head
The Commodore 1541 floppy drive is a real workhorse, that was used by millions of C64 users. It came with drive mechanisms from different vendors. The Newtronics/Mitsumi drive assembly has the annoying fault to have their drive heads fail due to some wires going open inside of the read/write head. This is so far not economically repairable. However a clever user by the nickname of Ruuudi on German Forum64 has designed a little bodge PCB to make the half of the head that is still okay to all the work and thus revive an otherwise dead drive.
ZoomFloppy+OpenCBM+8050
The main issue with the Commodore 8050 and 8250 drives is: How do you get data onto them? The units use 100tpi floppy drives that are incompatible to the regular 48tpi and 96tpi disk drives used in the 1541 and in PC DD and HD drives. So there is no chance using those. However there is the ZoomFloppy, which is an implementation of the XUM1541 interface and it comes with an optional IEE488 plug! We can attach the 8050 to that, and use the OpenCBM tools to read and write data to and from the floppies.
Let’s Code MS DOS 0x22: 2nd Reality Tunnel Effect
In 1993 the Future Crew released the seminal demo “Second Reality”. One of the more simple effects they showed in this demo was the “Dot Tunnel”. It is a simple, yet mesmerizing oldskool demo effect. We can build on our knowledge of fixed point maths to implement this effect and maybe even improve on the original!
The ReSeed SID Sound Card for the Plus/4 & C16
The Commodore 264 machines, which include the Plus/4 and the C16 used the TED chip for video and sound. The audio capabilities were not great: two square wave channels. The Commodore 64’s SID chip on the other hand was a proper three voice synthesizer. So back in the day people built expansion cartridges for the Plus/4 utilizing the SID and eventually games and demos using this were published. These cards are pretty rare, but now there is a homebrew clone of the card!