Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!mcsun!ukc!tcdcs!swift.cs.tcd.ie!vax1.tcd.ie!smcgerty From: smcgerty@vax1.tcd.ie Newsgroups: comp.sys.amiga.programmer Subject: Re: Copper SKIP does not skip WAIT!!!! Message-ID: <1991Mar4.095014.7896@vax1.tcd.ie> Date: 4 Mar 91 09:50:13 GMT References: Distribution: comp Lines: 49 In article , mt87692@lehtori.tut.fi (Mikko Tsokkinen) writes: > [Quote from HW ref. manual] > The skip intruction causes the Copper to skip the next insruction if video > beam counters are equal to or greater than the value given in the instruction. > > [Examples of CSKIP] > > CONCLUSION: SKIP INSTRUCTION SKIPS ONLY MOVE COMMANDS!!!!!!!!!!! > > This information is very important to if you are ever making complex > copperlists. Another bug in HRM1.3 (or in the hardware) in two days. Hang on, what's the point in skiping a CWAIT? CSKIP does everything a CWAIT can do. CSKIP is intended to be used as part of a CopperList REPEAT..UNTIL loop constuct, where it skips the 'GOTO' if the 'condition' is TRUE. I can't think of a CList which needs a conditional CWAIT, that can't just be expanded out or something. Memory's cheap!! 8-) > Please someone confirm (from CBM?) is the hardware working wrong or is the > manual wrong or is it just me. It _is_ a bit unusual though! That seems to imply that the Copper actually reads the instruction after the CSKIP while Waiting, and either jumps it or not depending: a) on the raster position (as per norm) and b) on the actual instruction read after the current CSKIP (a bit odd..) Now that I think of it, I remember someone telling me that it was _quite_ likely that the Copper _did_ read in the next instruction while waiting for a raster position to arrive. This is so that a CWAIT&CMOVE combination will have the CMOVE precalculated and 'ready to go' the _instant_ the CWAIT position arrives. Perhaps the 'bug' you noticed is intentional. Perhaps not! 8-) I'll try it on my Copper, how about some others trying it on theirs? The 'bug' might have been fixed. > > MIT > > -- > Bubble Bobble Stephen ---------------------------------------------------------------------------- | / T | / Stephen John McGerty | Amiga // | | / | |/ smcgerty@vax1.tcd.ie (C.Sci.) | "Hmm.. No, nothing." \\// | |__________________________________________|_______________________________| #! r