> The overscan trick was, I think, first discovered by NOP and used in
>"Unknown Reality" at the title screen. Achieving the vertical overscan
>on the V9938/V9958 is actually quite simple. You only need two line
>interrupts (using r#19) and flip the LN bit (r#9 b7). The LN bit selects
>between a screen height of 192 lines and 212 lines.
> The first line interrupt needs to be at a line before line 192 and it
>should set the LN bit (screen height = 212 lines). The second line
>interrupt should be at a line beyond line 212 and clear the LN bit
>(screen height = 192 lines). This will somehow 'confuse' the VDP and it
>will keep on displaying skipping the black border in Y-direction
>alltogether.
Sounds good. Will try this afternoon. Let you know the results. Thanks for
the info.
>Hey, I thought it was done by moving by moving the screen up
>first with the set adjust reg (18?). Then almost at the bottom
>of the screen the adjust value is changed so that the screen
>is totally down (in a screensplit, just before the end of the
>screen).
Mmm... perhaps another valid method. Will also try it. But I guess
something more than just moving the screen needs to be done since the same
bottom slice would be re-displayed.
I'd prefer the 1st method (if it actually works) since I don't like the
idea of changing the adjust register overriding user's preset and leading
to a non centered screen on some monitors.
>Yesss!!!
>
>Thanks! This is >>really<< cool!!!
>(where is it used, in which demo etc?)
Mmm... it seems many MSX users are not much familiar with those hardware
tricks like overscan and sprite recycling. That would explain those
sprite-free trends.
I've used systems far more limited than a MSX and I've seen them doing
things you wouldn't imagine (triple 50Hz full screen parallax scroll + 8
50Hz bitmap moving objects on a ZX Spectrum: check out COBRA (Ocean) by the
geni-genious Joffa Smifff!).
MSX has not been used to its full potential yet.
Kiss you lot.
--
Madonna Mark Two
"Martin Galway means to me what Elvis meant to Sigue Sigue Sputnik"
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