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Forums > C64 Coding > unemulated VSP graphical glitch ?

2023-05-09 21:18

Oswald

Registered: Apr 2002
Posts: 5126

unemulated VSP graphical glitch ?

Me doing VSP in the middle of the screen, need the VICII in idle state for this to work (or so I know) so I open a line that displays $3fff with "FLD", the VSP effect is achieved via a dec $d011, right after that in the following cycles FLI bug shows up, and after the FLI bug VICII returns to "normal" display.

however when using banks $4000 and $c000 also a 1 cycle wide black "bug" shows up too (before the fli bug I believe), but using banks $0000 or $8000 this doesnt happen.

vice 3.7 or hoxs doesnt emulate it.

possible explanation would be that VICII doesnt have the bus so reads $ff from non connected bus for ghost byte, but the used banks also control the behaviour.

edit: I have another VSP on the top of the screen done on the top border

2023-05-09 21:40

tlr

Registered: Sep 2003
Posts: 1807

Isn't this just the recently discussed anomaly here: Testers needed: unemulated DMA Delay Artefacts

2023-05-10 08:32

Oswald

Registered: Apr 2002
Posts: 5126

oh yes, it looks to be the same, sorry I have red that thread, but forgot about it, didnt realize when reading what exactly the bug does.

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