>Rather than a CDROM, is it not possible via hardware on a disk to set it
>to Read Only.
>If so then you could just flippa-de-switch when you need an update.
This is good. Consider this exapansion: A PC or whatever based system
with dual NICs acting as a firewall or filter. The basic system is on a
CD-ROM. A 3 1/2 write protected floppy is used for system parameters,
variables, and booting. A streaming tape drive equipped for forward/write only
is used for logging. No hard drive is necessary. With a 250 Mb streamer,
double speed CD-ROM, 486SX-33/8 Mbytes, mini-tower, mono-VGA, and keyboard
you are talking less than U$1000.00, maybe U$750.00. Tape read/parameter
updates are done on a "system console" that is actually a similar PC. Alarms
are sent to an external machine.
Personally, I think the CD-ROM idea is GRRRRRRRREAT.