pouët.net

Maybe I'm biased since I provided some of the photos, but the coder guys being able to get a plain MSX1 to show this many colors is amazing and pushing the machine to it's limits.

Yes, probably most non-MSX people have a hard time understanding what merit this demo could possibly have, but it's not only the number of colors, it's also the fact that poor old MSX1's "screen 2" graphics mode only allows 2 different colors (out of a fixed palette of 15 colors) inside each 8x1 pixel block.

We didn't want to have music, because on an MSX, interrupts must be disabled when loading from disk, because each manufacturer's disk drive requires different timings provided by the drive's own interface ROM routines. So we would have had to stop the music between pictures.

Basically it's 256x192 with 15 fixed (ugly) colors and one graphics page. Two colors for a 8x1 block. The vram is not memory-mapped but accessed through a port. Here with partial realtime updating 120 flicker colors are possible, but in addition to that there's dithering and interlacing to make the combinations smoother.

A standalone viewer for the images available now:
here

Flicker colors through page flipping definitely isn't an achievement, but there's other things like interlace, special dithering (in the converter side), realtime screen update and more involved. Screen 2 doesn't even have two pages to flip.

The demo needs an "MSX 1 and screen 2 for dummies" explanation. For example:
- On an MSX1, you have 16kB video RAM
- The video memory is not memory-mapped so the CPU can't just write stuff to it (like e.g. C64 or ZX Spectrum can), but you need to access it through IO port commands
- The VDP (video chip) is so slow that if you use 100% CPU, you can upload about 3kB of stuff during a 1/50s frame.
- Screen 2 (256x192 "multicolor" mode where you can have 2 colors out of 15 for each 8x1 block) doesn't have any "pages" because there's only 16kB of video memory
- Even if memory allowed, the VDP1 doesn't have page-flipping to begin with, no "scroll register" or stuff like that. The only thing you can do is flip the "name table" to another location, allowing you to change the contents of the screen without uploading data through IO commands, but there's only a single "character" (i.e. 8x8 block) space.