Re: [stella] Newbie Cycle Counting Question

Subject: Re: [stella] Newbie Cycle Counting Question
From: "Eric Ball" <ericball@xxxxxxxxxxxx>
Date: Mon, 14 Apr 2003 21:16:43 -0400
The Z26 trace file also has a wealth of cycle information, not only opcodes
but sprite positions as well.

A trick I use for most instructions is to count the number of memory
accesses.  So LDA (ZP),Y requires
1 cycle to fetch the opcode
1 cycle to fetch the ZP pointer
1 cycle to fetch the LSB
1 cycle to fetch the MSB
1 cycle to fetch the data
(Yes, I know that if the Y offset goes over a page boundary there's another
cycle, but you make sure your tables don't do that.)

For programming I am finding a simple spreadsheet very useful for creating
kernels.  Kind of Z26 trace in reverse.  I list the 6507 cycle numbers in
one column and pixel positions in the next, then put in the next columns
stuff like playfield starts or where I need to position sprites (with HMOVE
values).  Then I can start laying out the instructions in the next column
and easily move them up or down and see where I have spare cycles.  It's
also great if you are updating registers on the fly so you can make sure you
aren't updating too soon or too late.

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