V9990 setpage

By Ritter

Supporter (6)

Ritter's picture

24-06-2022, 16:12

Hi everyone,

I'm trying develop a new game for V9990 (Prince of Persia), and trying to understand how it works.
The game is using B1 mode, 8 bits, 64 colors, and the game do some copy commands.
Basically it saves the background, blit the player, blit the columns that are in front of player and so on.
The "problem" is: The player blinks a little (sometimes). On V9938 we use "set page" to write on a not visible page and show another page, but on V9990 I only found a SetScrollY routine.
So, I tryied to use this tecnique (SetScrollY), it shows the correct page, but switching it 15 times per second, just after the vblank, sometimes the screen appears to be "rolling" (up and down some pixels).
Any sugestions?

I can upload two videos, one without page switch and one with.

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By MsxKun

Paragon (1111)

MsxKun's picture

24-06-2022, 19:05

Ritter wrote:

Any sugestions?

Just one. Try pattern mode Smile

By Ritter

Supporter (6)

Ritter's picture

24-06-2022, 19:11

Thanks for answer.
screen "rolling" on "setpage" was solved now, the problem was one non-optimized routine. Now executing SetScrollY exactly on vblank, the problem desapeared.