oric_dan:
I'm kind of surprised that you guys are able to get 1-Mbaud comms at all.
I did not have any problems at 2 M either. The performance gain was marginal so I stuck with 1 M.
Namely, serial Rx is done using polled I/O and not interrupt-driven I/O, as far as I can tell, so I'm surprised the bootloader can even keep up with the incoming datastream, and not lose characters at those speeds, considering how the main-loop is written with so many if...elses that need filtering.
1 Mbps is 10 microseconds per byte which is 160 cycles. Seems reasonable to me.