In article ,
Keith F. Lynch wrote:
3) Redundant CPUs, one of which is running a different operating
system, so if the other two get frotzed by Yet Another Windows
Exploit in deep space, the Penguin can Save The Day...
Only if the Windows machine(s) haven't already fired the pyros, left
the gas valves open, pointed the camera at the Sun, etc.

Doesn't the Shuttle have three computers all running in parallel, with
majority vote ruling?

It's actually four, with elaborate arrangements for cross-connecting
things as desired. (There are only three of some of the more important
subsystems, so if one computer is acting up, you can cross-connect to put
the other three in charge of those.) The majority-rules voting is done
in hardware.

This works only because all four are running the *same* software, bit for
bit identical, in lockstep. You couldn't get the necessary low-level
timing synchronization on machines running different code.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |