[sdiy] Best software noise algorithm?

[Dave Manley]

Tom Wiltshire wrote:
> Hi All,
> 
> What's the most efficient software pseudo-random noise algorithm?
> ...
> 
> I'll be doing this in dsPIC assembly as usual, and I've currently got a 
> 64-bit LFSR that generates a new 16-bit number in 19 cycles. The quality 
> and sequence length of that are more than I really need, so I'd like to 
> speed it up.
> 
> Have people got any good tricks to share for making random numbers 
> quickly ?

I don't think you'll find anything more efficient than an LFSR. I assume 
you've already chosen a polynomial with a minimal number of feedback 
terms?  Perhaps you can do something memory (table) based, where you 
exor entries out of a table - but I don't ever recall seeing such a 
method, and you probably don't have a lot of memory to spare in the 
dsPIC.  A good reason to have an FPGA along with the dsPIC :0

-Dave

P.S. In the Mopho, one DAC is used for nothing but noise generation. 
It's a little funky, I need to study what going on a little further...