> Relay based, more reliable and needing less replacement than vacuum tubes I assume, Kinda sorta. Relays are mechanical devices that wear every time they're t

> Relay based, more reliable and needing less replacement than vacuum tubes I assume, Kinda sorta. Relays are mechanical devices that wear every time they're toggled. Every time you toggle a 1 to a 0 or vice versa, you risk destroying a relay. Vacuum tubes don't have moving parts, so the wear is significantly reduced. However, when they're on, they're very hot, so their wear is related to power cycling. Every time you power the machine or power the machine off, you risk destroying a tube. Colossus was kept in a powered on state 24/7, even when not in use, despite using an ungodly amount of power. It was a measurable proportion of all of the electricity used on all of Britain during WWII. So if you never run any programs on a relay computer and keep it in a low humidity basement, it will last indefinitely. But if you use it to do stuff, you'll be diagnosing and replacing failed relays routinely. If the computer has a clockrate of 10Hz and uses reed relays (the long life kind) with a lifetime of 10 million cycles, you can expect any individual relay to last 2,000,000 seconds of continuous use. Which is about 23 days. Multiply that by 1,000 relays and you've just figured out why it takes a full time employee just to keep the machine running. Imagine a RAID array using drives with a MTBF of 23 days. Eww.