But then it turned out not to be the load at all. No matter what I ran on that Pi, it would corrupt its SD cards in a matter of weeks (the symptom was that the fourth bit of some bytes would just stick on). I assume it was just something broken in the Pi itself.
You can simply root off of a USB disk by changing the "root=" parameter in cmdline.txt on the FAT partition on your SD card. Since the card won't otherwise be used unless you mount it if you do this, your next card should last forever. I've got a Suptronics x830 board and enclosure with an 8 TB drive which boots this way.
Any Pi processor newer than the original ARM1176JZ should run NetBSD pretty well. My 900 MHz Pi 2 runs NetBSD/vax almost as fast as a VAXstation 4000/30 (VLC), which is about 5 VUPS. An original Pi or Pi Zero should be able to emulate a VAX at least as fast as an 11/780.
One issue with CPU intensive things on Raspberry Pis is that even if your power supply provides plenty of current, the slightest drop in voltage can cause throttling. If you know your power supply is good but see a lightning symbol anyway, add "avoid_warnings=2" to config.txt on your SD card's FAT partition.
John
