Moon Cresta 7800

[Moon Cresta 7800]

Purely down to MARIA bandwidth. A graphics data access takes 3 MARIA clocks. If its 1BPP you read 8 pixels in that byte (40 reads to fill a 320 pixel scanline + DLL entry overhead). If its 2BPP you read 4 pixels per byte (40/80 reads to fill a 160/320 pixel scanline + overhead) and if its 4BPP you read 2 pixels per byte (80 reads to fill a 160 pixel scanline + overhead).

 

25,920 clocks (at 216 scanlines) w/o overhead on 1BPP - Jeebus. MARIA is what some odd 3Mhz, but I guess the DL/DLL overhead is a real killer, especially because of DMA. I might be getting that wrong though.

 

Nope! You can change mode per zone using a DLI but not use both modes in the same zone.

 

Well, crud. Color is a real killer for me, if I can get 25 at 160 but 9 at 320, I guess I'll have to stay in the low res realm. I was really looking forward to that too (hi res level, low res sprites w/ more color). I know I can do tricks to squeeze in more colors, but I'm just plunking around right now - kinda too advanced for me right now. BTW, what is the max (visible) vertical res in 160?

[Moon Cresta 7800]

320A is 1BPP so that gives you 1 colour in each palette and a common background colour to all palettes making 9 colours in total without using programmer tricks. With programmer tricks (DLIs) you can increase the number of colours on screen by changing palette entries on the fly on a per zone basis.

 

I wonder what the logic behind neutering color in 320 mode was? But 320A actually sounds more attractive, 8 pals, 1col, 1bg vs. 2 pals, 2cols, 1bg - 9 vs 5

 

hmmm... have an idea - is it possible to use 320A and a 160 mode simultaneously - like maybe draw a level in 320A and draw sprites in 160 (so they could be more colorful)? Or would that approach be more trouble than it's worth?

[Moon Cresta 7800]

@CrudOMatic: I used 320B mode, with Kangaroo off (Transparency on). I actually have the vertical resolution at 216, which is 40 vertical pixels (5 zones of 8 pixels each) shy of the arcade. I did away with the zones just above and below the score zone, the 'credit' zone at the bottom, and an extra zone at he bottom and extra zone at the top to make it fit. As far as the colors, With 320B/Kangaroo-off mode, you have two palettes with two colors each (the third color is not used). I used a few DLIs to change them mid-screen at specific places.

 

Nice method. I'm actually trying to read up on as much documentation as possible - would it have been better to use the 320A mode? I can't remember where I read it, but doesn't it give you 12 colors (4 palettes of 3 colors each), but with a funky data layout? Not sure if it was 320A, but I might be wrong about a 320 mode allowing 12 colors...

 

Also, it was my mistake on the vert res of 270 - I just measured the inside of the ProSystem window, which came out to 270

[Moon Cresta 7800]

How did you get the 320x270 resolution? with that many colors?