On Sat, 26 Aug 2000, you wrote:
> > In its current form, it produces numbers in the range 0..27, but you can
> > easily change that. You have to know that the middle bits of the seed are
> > the most "random", so use those for the result.
>
> Thanks Maarten. And yes, I knew that the middle bits of R were most
> 'random' but it just wasn't random enough for me.
I meant the middle bits of RandomSeed in the source...
The thing about R is that it's not random at all. It is just a very fast
counter. But because it's so fast and only 8 bits wide, it overflows very
often and therefore seems random. R is very useful to create a seed for a
random generator, but R not useful when you read it repeatedly.
Code like this:
ld a,r
ld b,a
ld a,r
sub b
will produce a constant number. I'm not sure if it's 100% constant, but it
will at least be around the same value. You can increase the value by putting
some NOPs between the two "ld a,r" instructions.
As far as I know, Z380 doesn't have an R register that actually counts (it's
always zero). So if you want your code to run on Z380 and some other
Z80-compatibles, don't use R as your only source of "randomness".
Bye,
Maarten
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