Tag Archives: Amiga

Phasor: An Atmel-flavored nostalgic demo

The demoscene is a computer art subculture specializing in producing demos, or audio-visual presentations. For the uninitiated, the demoscene first appeared during the 8-bit era, running on systems such as the Commodore 64, ZX Spectrum, Atari 800 and Amstrad CPC. In later years, increasingly sophisticated demos were coded for the Amiga, Atari ST and, yes, even DOS/Windows PCs.

Perhaps one of the most famous demos ever written was Second Reality by Future Crew. Coded for the Assembly ’93 demoparty, Slashdot voted Second Reality one of the “Top 10 Hacks of All Time” in 1999.


Although it is now 2013, some of us can’t help but get nostalgic for the demoscene days of yore. Fortunately, a talented coder named Linus Akesson (aka LFT) was kind enough to pen an old-style demo dubbed “Phasor” which runs off an Atmel ATmega88.

In the demo above, the microcontroller is clocked at 17.73447 MHz, exactly four times the frequency of the color carrier wave.

“In other words, four clock cycles per ‘color pixel,’ and in those four cycles one has to generate a sine wave with controlled amplitude, phase and constant offset,” writes Akesson.

“There is no chance of generating a smooth sine wave, because the CPU is limited to a maximum output resolution of one sample per clock cycle. Even this is not really feasible to do entirely in software, except for very basic visuals, such as a bunch of static color bars. But the effort can be cut in half thanks to a loophole in the PAL encoding scheme.”

Impressive, eh? Oh, and yes, here is Second Reality by Future Crew!

Atmel’s AVR ATmega644 powers this 8-bit retro gaming console

Written by Andreas Eieland

Do you remember reading comic books while waiting for your Amiga 500 to load the latest game, or the joy you felt when the first 8-bit Nintendo hit the streets?

© Bill Bertram 2006, CC-BY-2.5

I still do, and nostalgically remember a time when many of the games and hardware were simpler (streamlined), easy to understand and mod. I guess I’m not the only one who appreciates that the Amiga was equipped with sockets for the biggest components, making them easy to swap in and out.

Clearly I am not alone with my nostalgic thoughts, as a couple of years ago we had a “retro data party” at the Atmel office and people showed up with all kinds of old, dusty machinery. After drinking some beers and borrowing some components from our apps-lab we had almost all of them working and playing our old favorite games.

Now there is someone who has taken this concept a bit further with the creation of an open source 8-bit retro minimalist game console which is based on an Atmel’s AVR ATmega644.

The project is called the UZEBOX. It is easy to put together if you do not want to build the hardware from scratch, and uses a split software approach where sound and video generation are background tasks. Meanwhile, the games end-users develop in C exploit the complete interrupt system and numerous other resources. They have over-clocked the CPU “slightly” from 20 to 28MHz, but at room temperature, and not used in a life critical application like an airbag controller or Airline autopilot, this is really not a big deal.

As you can see above, there are several videos of the games on YouTube, and the UZEBOX crew even has a game design coding challenge going on right now.