esker@abaa.uucp (Lawrence Esker) (10/10/89)
In article <13370@nsc.nsc.com> chaim@nsc.nsc.com (Chaim Bendelac) writes: >I recently downloaded a game from a local bbs. It uses what I think >is a sprite in the form of a volleyball. However, instead of showing >itself in its round form, the ball is displayed as a ghostly white >stripe all over the length of my screen. I have tried "nofastmem" >but cannot get it right. I have seen this effect with other PD programs, >and I am starting to worry. Is there something wrong with my A500? No problems with your machine. You are using an overscan screen probably via MoreRows. There is some sort of contention problem between using Spites and overscan screens. I had always thought it was only when using all 7 sprites and overscan until the VolleyBall and PacMan games proved me wrong. I have always been meaning to get Commodore to tell me exactly where the problem lies, ie. ASIC's, Hardware, Amiga software, or improperly written user software. Hopefully someone a C= can give more detail and when the problems will be fixed. Until then, you can develop a special boot disk that is a normal 640 wide screen and play your sprite based games from it. -- ---------- Lawrence W. Esker ---------- Modern Amish: Thou shalt not need any computer that is not IBM compatible. UseNet Path: __!mailrus!sharkey!itivax!abaa!esker == esker@abaa.UUCP
new@udel.edu (Darren New) (10/10/89)
The problem is that the chip that DMA's the memory for the screen has only a limited number of fetches it can perform during HBlank. If you have a screen too wide, it will need to fetch playfield bits before all the Sprite bits are fetched, giving garbage in the final sprites. I think this is Agnus (Angus?). I don't think it can be solved w/o speeding up or widening the memory. -- Darren (But then, what do I know?)