DOS 8086 128B Animated Color Bars Demo
A 127 byte MS-DOS demo that draws four colored bars that scroll up
and down the screen.
Filmed using dosbox on Linux.
Sourcecode and Disk Image
You can get the disk image here:
colorb.zip (300B), 27 October 2020)
You can get the sourcecode
here in the seasons directory of
my dos_programs github repository:
git clone https://github.com/deater/dos_programs/
- 127 Byte demo targeting an 8086 with MCGA graphics.
This is similar to what you might find in the PS/2 Model 25
machines in the computer labs at my middle/high school (replacing
the Apple IIs)
- Was dusting off old code on mine from the 1990s where I did a lot
of inline assembly in Pascal based on the PCGPE.
- Waits for retrace which should give it consistent speed.
- Did a lot of tricks to get it to display the four color bars.
Including changing the direction flag.
- It is tricky trying to remember which instructions set the Zero flag
as the 8086 and 6502 are different in this regard.
- Most of my x86 assembly has been on a 386 or newer so it's tough
remembering which tricks won't work on the 8086.
- It's also a lot harder to optimize for size on 8086 than on 6502, there
are just so many complex instructions with complex size rules on
- In the end the 8086 does win for code density, I can't quite get more
than two color bars going on an Apple II.
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