Clarify serial number format
Framebuffer iterator scheme, to avoid division

This actually makes us slightly slower, due to increased register pressure, but I think if I can alleviate that we'll see a speedup.
Another optimization attempt. Still not helping.
Revert "Another optimization attempt. Still not helping."

This reverts commit f5e7cc2ea360ecf9650830f1857d02198f5d6959.
Revert "Framebuffer iterator scheme, to avoid division"

This reverts commit 07106959f6340912fc47c94ee40cc072479ec44e.
Move pResidual calculation up one level

This amazingly helps quite a lot! The idle time between frames is down from 0.8ms to 0.66ms now.