30 Jul
2004
30 Jul
'04
9:43 a.m.
The standard "clock" was the KW11-L -- just
an interrupt tied to the
mains frequency. That was a very common option in early machines and
became a builtin feature of the CPU assembly in later ones.
Some systems, for example those used in real time control, might have
a KW11-P -- which lets you program the interrupt rate from a choice of
three input oscillators (100 kHz, 10 kHz, and mains, if I remember
right) along with a programmable divider. The 11/20 on which I
learned in the college physics department had such a beast, and I
added support for it into RT11 BASIC.
I know both of those cards, along with the DL11-W (which essentially has
a KW11-L built-in), the MNCKW (MINC clock module, somwwhat similar to the
KW11-P, the KW11-K (IIRC that's a dual clock card with some nice
features), and so on. I think I have prints for all of them too.
However, I don't think this is what Sellam meant by 'real time clock'. I
think (and please correct me if I'm wrong) he was talking about a
Time-of-Year clock type of thing.
Finally, there's the KW11-C which is what I was
trying to remember.
That is a TOY clock. See
Ah, now that one I've not come across.
-tony