First computer with real-time clock?

From: Tom Jennings <tomj_at_wps.com>
Date: Thu Jul 29 14:50:34 2004

On Thu, 2004-07-29 at 04:49, Vintage Computer Festival wrote:

> It's come up in some litigation. The actual issue at hand is that someone
> was able to overturn a patent by claiming the IBM 650 had a real-time
> clock built in. They "proved" this by submitting as evidence a printout
> that had the date printed on it(!) I've checked the IBM 650 Manual of
> Operation and it makes no mention whatsoever of a real-time clock. I
> pretty much figured it wouldn't but I of course had to do due diligence.

Oh this makes it more interesting! I know that I have a book that
discusses the development of this, in practical terms, it would be
mid/late 1950's. It would take some research to find it.

Certainly there were time-periodic interrupts for isochronous purposes
by 1960, whether the 650 had one or not.

"Keep time when the power is off" -- umm kids, for giant old machines,
turning the power off was like a massive emergency/annual maintenance
event/likely disaster/call-the-boss-up-at-3am, retaining the time would
be looooow on the list of things-to-worry about.

1970's DG RTOS and RDOS, for example, supported time-of-day, maintained
by the RTC option on the CPU board -- which option was some TTL chip and
a crystal. It generated a periodic interrupt. Upon shutdown/reboot (it
was a small mini, no catastrophe :-) you'd enter the date & time.
Received on Thu Jul 29 2004 - 14:50:34 BST