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Mace
Registered: May 2002
Posts: 1799 |
Ghostbyte / garbage / $3FFF
Discussion about the ghostbyte in the comment of Aliens:
Quoting Jammerso for what extent can i control this 'garbage'? in terms of chars and colours.
The ghostbyte is always black.
It occurs in the upper and lower border, when opened, but also in the 'void' that is created with an FLD routine.
If you want that effect as seen in Aliens, you have to write values to $3FFF in a raster routine.
The byte is repeated over the entire width and height of the borders, as the patterns shows.
BTW, I can't remember ever seeing a 'split raster' in $3FFF...
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w4rp8
Registered: Oct 2010
Posts: 9 |
If it's not a bug in Vice. And the timing of the glitch seems to shift with the index of the color-register you write into. |
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Compyx
Registered: Jan 2005
Posts: 631 |
Quoting KrillYou both seem to be ignoring or misreading what w4rp8 is implying here.
If i understand correctly, this is about glitching the rendering of the idle byte by just writing to seemingly unrelated colour registers, and that glitching causes it to be briefly rendered with black hires pixels in multicolour mode rather than black brick pixels.
And that would then display some multicolor pixels in a single 'char'? |
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Copyfault
Registered: Dec 2001
Posts: 467 |
Quoting Krill...
If i understand correctly, this is about glitching the rendering of the idle byte by just writing to seemingly unrelated colour registers, and that glitching causes it to be briefly rendered with black hires pixels in multicolour mode rather than black brick pixels. Oh that sounds like "something new"... good point, will have to investigate deeper on this "feature".
Thanks for bringing it up, Warp8! |
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chatGPZ
Registered: Dec 2001
Posts: 11148 |
I strongly suggest to try it on real hardware, and come up with a test program :) |
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Krill
Registered: Apr 2002
Posts: 2854 |
Quoting w4rp8If it's not a bug in Vice. Yes, of course. That manipulation apparently only triggering line-wise responses makes it reek a bit like an emulation bug, indeed. And what Groepaz said. =) |
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tlr
Registered: Sep 2003
Posts: 1727 |
I'm not sure I fully understand the description, but I'm assuming you're running x64sc right?
A simple screen shot of the effect would be a good start. |
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Laurent
Registered: Apr 2004
Posts: 40 |
This is from a real c64 (so, same behavior as Vice)
Fresh has some explanation here GhostbyteInSprite |
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tlr
Registered: Sep 2003
Posts: 1727 |
Quote:
This is from a real c64 (so, same behavior as Vice)
Fresh has some explanation here GhostbyteInSprite
If it's that, we have discussed it quite a lot here: Sprite data fetch in sideborder
From the description I thought w4rp8 referred to the screen area idle fetch graphics, not the idle part at the top of sprites. |
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Laurent
Registered: Apr 2004
Posts: 40 |
Thanks for the link TLR :) |
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w4rp8
Registered: Oct 2010
Posts: 9 |
Quote: Uhm, that isn't quite correct.
Ghostbyte has nothing to do with any color registers, it simply takes the last byte of a VICII bank, or when using ECM it 'folds' the last charset RAM into $01ff and thus uses $39ff vs $3fff or $79ff vs $7fff.
When you use hires ($3x at $d011) and single color ($0x at $d016), the upper and lower border will always be black*.
* = when opening the upper/lower border.
Your reply is actually true as the effect does not show up in x64sc when I checked now. So I highly assume that it’s also not gltching on the real hardware. Sorry for rising false hopes ;-) |
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