I have written a little program which outputs PCM audio by mixing four sinewaves with different amplitude and phase (4 phase accumulators run in parallel with envelope data stored in arrays). Timer 0's OVF interrupt calculates the new output amplitude at a frequency of F_CPU/256 (actually it happens at half that freq because the interrupt takes more than one period to complete). Anyway, it works just fine on a 328.
When I take the same code (with minor adjustments in the setup department to cater for different pin and port numbers) and build it for a TINY device, I get audio which is slow and staticky sounding and where the frequency hops around where it shouldn't. It appears I have plenty of memory on the TINY85 at least. Can you think of any reason why the TINY would not be able to perform this kind of task under the same conditions clock speed etc, as the MEGA?
At this stage I am just interested to know if there are some inherent limitations or inabilities of the TINYs of which I'm unaware.