On 7/1/2017 8:59 AM, Noel Chiappa via cctalk wrote:
> From: Jerry Weiss
> So it would appear the upgrade board makes provisions for both
> situations.
I'm not sure that the two situations that the upgrade board supports are in
fact different, from its point of view. (Assuming that the two situations you
refer to are the two different consoles.) Yes, the _system_ supports two
situations: i) the KY11-LA connecting directly to the backplane, and ii) the
KY11-LB going via the M7859; but the DEC CPUs don't seem to draw any
distinction between the two.
Looking at the KY11-LA prints, the connector to the backplane cable (the one
which is unused with the KY11-LB) carries signals like "Halt Request" and
"Halt Grant", which are generated in the M7859 (which has its own direct
backplane connection) when using the KY11-LB.
So as far as the consoles are concerned, those signals come to the backplane
via different paths, but as far as the CPU is concerned, it sees the same
things through its backplane connection, no matter which is in use - so how
would the upgrade board be any different?
Since I feel like I'm talking to a wall here, let me explain how things
are set up.
In the original 11/34 configuration you have (from slot 1 on down)
1 - M7266
2 - M7265
3 - M9301/M7859
4 - SPC/MUD
The front programmer's panel is connected via a 20-pin cable to the
M7859 in slot 3.
With the upgrade installed, you have:
1 - Empty
2 - Empty
3 - Upgrade CPU
4 - Upgrade Memory
The front programmer's panel is connected via a 20-pin cable to the CPU
in slot 3.
The M7859 is removed from the equation. There is nothing to provide the
front panel signals to the backplane, so the header on the CPU board is
(apparently) used to take care of this. This is backed up by the
observation that *if the 20-pin cable is disconnected, the front panel
does nothing and if it is connected, then the HALT/SS and BOOT switches
are functional*. Nothing else on the programmer's panel appears to do
anything, and that doesn't surprise me.
There is also a 10-pin header on the CPU. I do not know what it is for,
but Jerry's suggestion sounds valid. It does not appear to be a serial
port; there's nothing that looks like a UART onboard. I've spent a
couple of minutes trying to trace things out but I haven't made much
headway. This board is dense and multilayer and nothing in the
immediate area seems to connect to it.
The _only_ cable(s) that ever connect(s) to the CPU board (in the KD11-D or
KD11-E) are from the KY11-LB: those cables are the ones that carry the signals
to support the microcode single-stepping. How would the upgrade board use
these?
Yes, the 11/34 CPU didn't connect to the front panel in any way. I
don't understand why this precludes a CPU upgrade that replaces large
portions of the original hardware from doing so in order to support the
front panel in a minimal way.
One thing that might help untangle the function of those two headers on the
upgrade board is to look and see what chip(s) they connect to. If they aren't
EIA transmitters/receivers, yes, they aren't serial lines. (I only suggesgted
that because I couldn't figure out what _else_ they could be.) Can that be
done?
See above.
- Josh
Noel
