Look for an ESCC version they have deeper fifos.
> Does anyone have experience with these devices at this speed? Is Linux
> up to this sort of I/O load? Should I even be considering doing it
> this way?
The biggest problem you will have in sync mode is the tx underrun
problem. You need a deep tx fifo to avoid sending aborted sdlc frames.
An SCC wont work on a system with more that 2 char time interrupt latency.
The ESCC has deeper tx fifo and that *may* work. If you want to use an
SCC for 64k+ sync on a PC you need a card with DMA; that avoids all the
underrun issues.