Honored Contributor
Honored ContributorThe Nios II/f pipeline is optimized for hitting in the D-cache. If you disable the D-cache using always_bypass_dcache,
the Nios II/f takes one cycle longer than the Nios II/s to perform loads and stores. This could reduce your performance but I'm surprised it is being reduced 10X. BTW, the upcoming Nios II release has a better mechanism to disable the D-cache which also removes the extra cycle of penalty. The other difference between the two is that Nios II/f has dynamic branch prediction whereas Nios II/s has static branch prediction. Dynamic branch prediction tends to offer better performance for most applications. Maybe your application is an exception? Even still, I'd be surprised to see a 10X slow down. Do you need more performance than the Nios II/s provides or are you just sharing your surprise at the outcome of switching to a Nios II/f?
