Poll: most challenging game that could be ported to msx in the'80

on msx1 is more challenging to do. on msx2 there is already a outrun that is not so good because of sloppy implementation.

ok can we exp!ain briefly because it is challenging? (For example: memory, speed, vdp,etc)

Another one that comes to mind is "Stunt Car Racer", since the VDP of the MSX 1 is really not the best when it comes to 3D rasterization algorithms I think it would be quite a challenge to port this one! there was a ZX Spectrum version that was pretty good though!

Even the C64 version isn't that bad, and that thing doesn't even run at 1Mhz in PAL territories. Different CPUs, etc, but a sub-1Mhz 6502 is definitely slower than a 3.58Mhz Z80.

A serviceable MSX port could be achievable by a talented and dedicated programmer though, as it looks to be playable even when only somewhere in the 5–10 fps range (different times, different standards, etc), and — having just measured it — the Spectrum display window is only somewhere around 224x144 pixels, so a little less than 4kb for the animated region.

On the CPU side you'd run a pretty simple split process, whereby the main thread of processing generates the next frame, and an interrupt routine shovels the most recently completed frame to VRAM for as long as fast access is available, then returns and lets frame calculation continue until the next interrupt. Theoretical maximum on an NTSC device: 12fps, with a bit less than 30% of CPU time lost to VRAM pushing. Of course, the interrupt routine would return immediately if a next frame weren't available yet and 12fps is very optimistic so you'd end up with a number somewhere less than 30% in real life.

The main problem would be squeezing two video buffers into VRAM. You might need to be smart enough to generate a tiled display directly for screen 1, otherwise I guess it's one of the undocumented half-bitmap arrangements of screen 2 that breaks you on an MSX 2. So, ummm, implement a separate MSX 2 version that's graphically better all around?

The actual 3d plotting is relatively simple on that title, at least. On the 8-bit versions there's an assumption that you're generally upright or close enough, so for each floor section it just fills from the top of the polygon down to the bottom of the screen and then draws the vectors on top. Only the top sections of the track get the real 3d maths applied, the sides and bottom are just sort of implied by the fill-to-the-bottom trick. So most views are maybe a dozen vertices at most. Which would help a lot with a hypothetical screen 1 adaptation since tiles make for fast area fills.

Am I dedicated enough to test this assertion? Almost certainly not. It's armchair work at best.

The vdp hybrid screen 2 mode works on msx2 too. It does not work on some vdp clones