Subject: Re: [stella] Asymmetrical Reflected Playfield From: "Thomas Jentzsch" <tjentzsch@xxxxxx> Date: Fri, 21 Sep 2001 09:44:41 +0200 |
Glenn wrote: > If someone can explain what's happening at the tail end of the scanline for > why I don't seem to have as many cycles left as it seems, I'd appreciate it. I'll try :) 1. You have an error in your cycle counting, the second write to PF2 needs 3 cylces, so this operation ends at cycle 48 (not 47). 2. You have to count the additional code arround your PF-writes too. The maximum cylce count for this is 27 (19 before, 8 after the PF-writes). So, you need a total of 48+27 = 75 cylces. That's why any additional nop will break that kernel. But there might be (as always :) some optimizations possible to reduce those 27 additional cylcles. Examples - You don't have to decrease scanLine every loop, it would be enough to decrease only when X reaches 0. This requires just a different scanLine starting value. - You could use Y to save more cycles. - It might be also possible to avoid WSYNC by making the cycle count constant. But that will make the kernel very fragile, so I would do that near the end of the optimizing process. - Put the 3 nops directly behind WSYNC and join those free cycles with the other free cycles before WSYN to gain more flexiblity here. - ... Have fun! Thomas _______________________________________________________ Thomas Jentzsch | *** Every bit is sacred ! *** tjentzsch at web dot de | _______________________________________________________________________ 1.000.000 DM gewinnen - kostenlos tippen - http://millionenklick.web.de IhrName@xxxxxx, 8MB Speicher, Verschluesselung - http://freemail.web.de - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
[stella] Asymmetrical Reflected Pla, Glenn Saunders | Thread | Re: [stella] Asymmetrical Reflected, Glenn Saunders |
Re: [stella] asymmetrical playfield, Glenn Saunders | Date | Re: [stella] New idea for 6 channel, John Saeger |
Month |