KM11 Clone

[Tony Duell]

> 
> 
> Guy Sotomayor wrote:
> >
> >If I can get a preliminary count of folks who want one (or two or ...) I
> >can get the boards and parts ordered.  I'd like to place the orders
> >during the first week of January.
> 
> I have to plead ignorance.  I've got an 11/34 and an 11/44 (doesn't everyone?)
> 
> why do I want an KM11?

I'm pretty sure you don't, unless you have an RX01 (not an RX02) floppy 
drive, an RK11-C (or RK11-D?) DECpack controller, and maybe a few other 
peripherals.

 
> (I'm happy to believe I really do and just don't know it, but I need some
> coaching - I don't even know what it really does - can you write up a short
> FAQ for the clueless?)

The KM11 (original and clone) is a module with 28 lights (originally 
bulbs, my clone, and I assume this clone, uses LEDs) and 4 switches on 
it. It fits into a specially wired connector in some older CPUs (the 
11/34 and 11/44 are not among them) and peripherals, whereupon the lights 
monitor certain internal signals (perhaps the CPU microcode program 
counter, carry flag, xero flag, and so on) and the switches let you do 
things like single-step the microcode. If you are interested in figuring 
out exactly what goes on at the microcycle level, or want to do hardware 
debugging, it's a very useful tool. If not, then you don't need one.

Incidetnally, some machines have 2 connectors for KM11s (the 11/45 has 
one for the CPU, one for the FPU), so you might well want 2 of them.

I doubt, alas, if I'll be buying any of the clone boards. I have my 
hand-wired one (that really started all this, I guess) and 2 genuine DEC 
ones...

-tony