Random number generator (very fast - very basic)
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(New page: Random number generator (very fast - very basic) I saw a nice 6502 random number generator this morning, but at thousands of cycles per call, I thought a faster one might be useful here. ...) |
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| - | See the forums for a BBC sample program | + | See the forums [http://www.retrosoftware.co.uk/forum/viewtopic.php?f=73&t=640] for a BBC sample program, .ssd and discussion. |
Revision as of 09:20, 29 June 2011
Random number generator (very fast - very basic)
I saw a nice 6502 random number generator this morning, but at thousands of cycles per call, I thought a faster one might be useful here.
This is about the fastest random number generator you can get although it is really just a sequence of 256 numbers using 14 bytes (code and data if seed is in ZP).
Each call of rand will return A with the next of a 256 number long sequence of random numbers.
You can change the multiplier (5) and the addition (&45) to many different pairs and get different sequences.
One drawback of this method is that the lsb toggels each call - to avoid this, you could use a 16 bit number and take a selection of bits from the middle.
.rand LDA seed ASL A ASL A CLC ADC seed CLC ADC #&45 STA seed RTS
See the forums [1] for a BBC sample program, .ssd and discussion.