In S5 we use widely 76k8 packet using S5 version of
Main trick on HW is to replace 4.9 MHz XTAL with 9.8 one and
tell SW it has 4.9 MHz and 38400 bps speed.
It works with Linux SCC drivers, TFPCX, Flexnet SCC drivers etc.
On 1.2 Mbit/s links we use DMA card, of course. Even if it
may be possible to run it with IRQs (After I've seen some
HB9JNX code I will never AGAIN said: "this can not be run on IRQs"),
it is easier to modify Pi-card drivers as to go to own SW.
More info about S5 HW/SW is on http://www.hamradio.si