First computer with real-time clock?

Vintage> On Wed, 28 Jul 2004, Marvin Johnston wrote: Vintage> I'm thinking farther back. Was there any mini or mainframe Vintage> that had a real-time clock built in or as an add-on option? Vintage> It's come up in some litigation. The actual issue at hand Vintage> is that someone was able to overturn a patent by claiming Vintage> the IBM 650 had a real-time clock built in. They "proved" Vintage> this by submitting as evidence a printout that had the date Vintage> printed on it(!) I've checked the IBM 650 Manual of Vintage> Operation and it makes no mention whatsoever of a real-time Vintage> clock. I pretty much figured it wouldn't but I of course Vintage> had to do due diligence. Vintage> But it made me wonder: what was the first computer to have a Vintage> built-in real-time clock? I second the question -- defined how? For answering the litigation, you'd really need to know that... If the answer is: a device that maintains the time of day independent of the computer power, the oldest I know of is the DEC KW11-W (?not sure about the suffix). I don't remember when that came out, but it probably predates microcomputers. It wasn't a popular option. Another example, from roughly the same era, is the TOY clock in the Pro-350. That's a microcomputer chip, so presumably some PC type system offered it as well. (That may apply to the KW11-W as well... I don't know.) On the other hand, if the definition is a device that allows the computer to keep time while it is powered on -- which is all that you can deduce from the 650 example you quoted -- then certainly it goes as far back as the CDC 6600 (1964) and probably a lot further. Then again, that's after the IBM 650. By either definition we're talking about something that came out well over 20 years ago, so it would be "prior art" invalidating any current patent. paul