Both run on 6502 processors.

Code #1 is a delay loop.
Code #2 is a 16 bit unsigned multiply (multiplies $20/$21 by $22/$23, returning the result in $24/$25/$26/$27).

Update: OK, I couldn't resist. I dug out the 6502 assembler and emulator to test code #2. Now, admittedly, the emulator could be broken, but I didn't get any results that made sense for either a multiply or divide. I spent about 45 minutes playing with this, and the simulator seems to be executing as I would expect. But the resulting $26/$27 locations never come up with any valid values using $20/$21 and $22/$23 as inputs (the higher address is the high byte of each word, so I had byte ordering correct).

And since code #1 was going for maximum delay, you could have gotten a little more delay by changing it to: 
start	LDY #$FF    
loop1	LDX #$FF  
loop2	DEX       
	BNE loop2  
	DEY        
	BNE loop2  
	RTS
You're resetting X to #$FF, when it's already 0, losing 255 free 2 cycle delays.

--Chris

e-mail jcwren

In reply to (jcwren) RE: (2) What was your first program? by jcwren
in thread What was your first program? by Ovid

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