Crashing systems with serial line loopbacks....

[WA7KGX]

I should suspect the cards' drivers.  Using a Stargate Plus-8 dumb card,
I looped back a 1 meg file at 38400 bps, with average throughput more than
3000 characters per second, without any sign of distress.  This is with a
33 mHz Micronics motherboard, your mileage may vary.

I can't recall a problem with serial I/O crashing SCO *nix since 286 flavors
(possibly modulo beta test versions).