A long time ago, I was a MSX and MSX2 programmer

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By PingPong

Prophet (3789)

PingPong's picture

25-12-2012, 10:44

Maggoo wrote:

Actually i do remember from my old days that disabling sprites would cause problems when updating R18 multiple times during the screen refresh. No idea why, it just does (had the problems with multiple effects). Enabled the sprites and the problem was gone.

Would been too nice. The problem is still here with or without sprites enabled.

By Manuel

Ascended (18234)

Manuel's picture

26-12-2012, 20:39

Reminds me of the Sand Stone waving logo issue. It would show background color at certain lines, but only when sprites were OFF....

By ARTRAG

Enlighted (6564)

ARTRAG's picture

26-12-2012, 22:17

Playing around the R#18 glitch I ended with this
https://docs.google.com/open?id=0Bx4kWAc-fapqOW1LZl9QeWp3Um8

I tested it in z80 and r800 mode on real hardware and it works fine except for few sparse black dots here and there

The very interesting thing is that it works well on openmsx and not at all on bluemsx, where all copy commands are disrupted.
It is a true pity that the development of bluemsx was discontinued, anyway this is a nice example that shows the need of a severe tuning in the emulation of the vdp command of bluemsx (probably the failure is matter of wrong timings)

By PingPong

Prophet (3789)

PingPong's picture

26-12-2012, 23:15

ARTRAG wrote:

Playing around the R#18 glitch I ended with this
https://docs.google.com/open?id=0Bx4kWAc-fapqOW1LZl9QeWp3Um8

I tested it in z80 and r800 mode on real hardware and it works fine except for few sparse black dots here and there

Artrag, did you tried my last file? i expect no corruption at all and a running command. on my machine there was no corruption for almost 2:00 minutes.

By hit9918

Prophet (2909)

hit9918's picture

27-12-2012, 04:22

@ARTRAG,
I see a rare full height black column in both emulators.
I am confused, I thought that issue was gone.

another detail: this happens on on openmsx MSX2:
the first line of the split flickers if the ship is turned right.
but not when it is turned left. then it stops in a different xpos.

why does the stability of the begin of the split depend on variables
that get relevant two scanlines later.

By ARTRAG

Enlighted (6564)

ARTRAG's picture

27-12-2012, 10:02

The full height black column you see is a bug in the scrolling logic.
It happens when you change direction and the end of the level is displayed in the middle of the screen (the level is made circular, so there is some bug in my code where I wrap the level and the scroll changes direction).

About flickering, it has to be some timing problem.
It is usually solved by leaving a black line in the border of the score panel.

By ARTRAG

Enlighted (6564)

ARTRAG's picture

27-12-2012, 23:35

Pixel perfect screen 8 scrolling tested and perfectly working on real HW !
https://docs.google.com/open?id=0Bx4kWAc-fapqajc1Nld3enRZdEU

Any vdp glitch during copy has been avoided with to tricks, In the current code R#18 does never change while the copy engine is active. It is trivial but perfectly working.
As general note about the used trick, I can tell that if you aim to full frame rate, all vdp commands have to be shorter than one frame, so it should be possible always to arrange things in order to set R#18 between two vdp commands belonging to the processing for the next frame.

Sources are included and the code has been tested both on z80 and r800
Note BLUEMSX does not support this code due to timing errors in its vdp emulation.
Use openmsx or real HW

By mars2000you

Enlighted (6014)

mars2000you's picture

27-12-2012, 23:56

ARTRAG wrote:

Note BLUEMSX does not support this code due to timing errors in its vdp emulation.
Use openmsx or real HW

Are you sure ?

http://www.youtube.com/watch?v=WEDaGspUy8Y

By ARTRAG

Enlighted (6564)

ARTRAG's picture

28-12-2012, 00:23

which bluemsx version do you use?
I use
Versione: 2.8.3
Build: 34031
Data: 12/30/2010 9:44pm

and get this :
http://youtu.be/s8tbKZc8cdE

By mars2000you

Enlighted (6014)

mars2000you's picture

28-12-2012, 00:21

a beta of blueMSX 2.9

You could contact Daniel Vik to get a beta, it should be more positive and efficient than always complaining on a site that he does not visit (I don't know the reason).

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