Chris check out the thread
http://www.biglist.com/lists/stella/archives/199805/msg00090.html
Cheers
A
----- Original Message -----
From: "Christopher Tumber" <christophertumber@xxxxxxxxxx>
To: <stella@xxxxxxxxxxx>
Sent: Friday, October 18, 2002 8:01 AM
Subject: [stella] An Efficient Waste Of Time
> One thing I've found... annoying if wasting a bunch of ROM space doing
noting. That is, burning cycles for timing purposes but at the cost of ROM
space. Ideal solution would be various flavour NOPs, all using 1 byte but
consuming 2-a bunch of cycles. Unfortunately that's just not the case.
>
> So these are the instructions and instruction combinations that I've been
using to waste cycles. Anybody have any better ones?
>
>
>
>
> --------------------------------------------------------------------------
>
> 1 Cycle (0 or 1 byte)
> .w (Make a zero page instruction an absolute instruction)
> or
> ,x (Make a zero page or absolute instruction an indexed instruction)
>
> Notes: .w adds a byte of code.
> ,x needs x=0 (can also use y register)
>
> --------------------------------------------------------------------------
>
> 2 Cycles (1 byte)
> NOP
>
> --------------------------------------------------------------------------
>
> 3 Cycles (2 bytes)
> STA $ZeroPage
> or
> LDA $ZeroPage
> or
> DOP $ZeroPage
>
> Notes: STA/LDA Destroys register or RAM location (use scratch variable)
>
> --------------------------------------------------------------------------
>
> 4 Cycles (2 bytes)
> NOP
> NOP
>
> --------------------------------------------------------------------------
>
> 5 Cycles (2 bytes)
> dec $ZeroPage
>
> Notes: Destroys RAM location (use scratch variable)
>
> --------------------------------------------------------------------------
>
> 6 Cycles (3 bytes)
> NOP
> NOP
> NOP
>
> --------------------------------------------------------------------------
>
> 7 Cycles (2 bytes)
> PHA
> PLA
>
> Notes: Don't overflow stack
>
> --------------------------------------------------------------------------
> 8 Cycles and more - combinations of the above, or loop.
>
>
> [You can use PHA/PHP (1 byte 3 cycles) or PLA/PLP (1 byte 4 cycles) alone
but you have to be carefull not to mess up your stack (PLP/PHA would be
usefull if you have no stack!)]
>
>
>
> Chris...
>
> --------------------------------------------------------------------------
--------------------
> Archives (includes files) at http://www.biglist.com/lists/stella/archives/
> Unsub & more at http://www.biglist.com/lists/stella/
>
>
----------------------------------------------------------------------------------------------
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
