28 Jul
2004
28 Jul
'04
7:35 p.m.
Andy Holt wrote:
Depends a bit on what you mean by "real time
clock".
In earlier days the (salesman's) definition would include a line frequency
interrupt.
Under that definition most, if not all, 3rd-generation mainframes had one as
standard. For most pre-LSI minicomputers it was likely to be an option
rather than standard.
It goes further back than that. The 7094 modified for CTSS had a
periodic interrupt.
I assume Sellam means a device which will present the time and possible
date maintained independently of the CPU. There I would agree I we are
into the mini era if not the micro.... There was an add on RTC clock
card for the PDP-11 (but Sellam specified "built-in" ;-) If it does not
have to be built in I suspect you could find some earlier examples. ISTR
hearing somewhere of units which attached to mainframes which would
provide tame and date...
-- HansP