Subject: [stella] correction to my comment on matt's code From: Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx (Eckhard Stolberg) Date: Tue, 15 Oct 1996 02:29:32 +0200 |
Hello matt and everybody, I checked the sample.a65 program on the CD and noticed that it has the same timing errors. So everybody else: better not use it as a model for your own code. I also checked your (matt) code and noticed, that you are doing the overscan (accidently ?) right. The loop, where you wait for 32 lines does this. You could replace it with a routine that sets up the Tim64T timer with #35 (for NTSC; #42 for PAL) and waits for it to expire. This way you could do some game logic between the setup and the waiting. The routine that claims to do the overscan (between the TOP: label and the next BNE @1) is completely obsolete. All it does is filling a couple of ports with zero. This is stupid, because this way you have to reset things like the backgroundcolour again in every frame. You don't even have to call it once, before the first frame, because writing zeros to all ports is allready done by the very first loop in your code. I think, you could speed up the loop that fills the RAM with zeros a bit(in case you need to use it in a more timing critical place) by replacing the STA 0,X with a PHA. Because the stackpointer points to the end of the RAM and is only one byte large, pushing zeros 256 times to the stack would cause the stackpointer to be the same as before and all the ports and the RAM to contain zeros. In your matt.a65 program you use ADC #1 a couple of times. They could be replaced by INC for speed reasons. But I think you allready know that. Also your programs are so small, that you could make them 2k instead of 4k, before you post them. For everybody, who wants to make matt's programs at least display right: You can easyly replace the second LDA #$05 line in all his sourcecodes with a LDA #43 line (LDA #53 for PAL) and recompile them with ASM6502.EXE from th CD. I hope this is at least a little bit helpfull to some of you. Ciao, Eckhard Stolberg 2stolber@xxxxxxxxxxxxxxxxxxxxxxxxx
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