On Mon, Feb 13, 2017 at 1:22 PM, Noel Chiappa <[email protected]> wrote:
> > From: William Degnan > > > PDP 11 KE11E M7238 EIS board (for PDP 11/40) which causes the CPU to > > crash when installed; front panel not responsive > > ... > > I installed a removable jumper so I can flip jumper configs back and > > forth between EIS installed/not installed. Without the EIS the system > > works fine > > To understand this symptom, one needs to understand how the EIS interacts > with the main CPU. Both include microcode, and what is supposed to happen > is > that when an EIS instruction happens, control is passed to the microcode on > the EIS board (the actual microcode words being fed back to the main CPU > through those three over-the-back jumper cables). The microcode on the EIS > board can then control the data paths, etc in the main CPU, to feed the EIS > data, and take back the results of the computation performed on the EIS > card. > > I'm trying to understand what W1 does, but I'm not there yet. It's shown on > the KD11-A print K3-8 (pg. 48), in the lower left corner, but its effects > are > somewhat obscure. > > To start with, the array of odd chips E6-E7 (74H60's) and E17 (74H53) are > expandable AND-OR gates. I'd never seen these before, but the lines running > to and from pins 11 and 12 on the 'H53 join the other three gates below it > into it - i.e. that whole array of AND gates all feed into one NOR gate > (output on pin 8 of the 'H53). > > So far, so good, but from there I'm still lost. When W1 is inserted (no > EIS) > it grounds the signal ECIN00, which comes in from off-board (as shown by > the > "A05S2", which is the pin it arrives on). The output of that giant NOR gate > is CIN00, which is immediately sent off-board (pin 'A05P1'). I have yet to > try and chase these signals down, and work out what they do; the KD11-A > Tech > Manual is fairly cryptic on the subject. > > Note also that, IIRC, the front console operates under control of > microcode. > > So I'm _guessing_ that what is happening is that somehow the EIS is, when > enabled, messing up the operation of the microcode in the main CPU, causing > it to freeze. > > > > Probably would not be a bad idea to test the cable and the connectors as well as the board. There could also be a fault with the UWord module (M7232) associated with signal processing too.
