This is from memory, and complicated by the fact that I work from the HPCC diagrams, not the patent. The former were drawn out before I'd come across the patent, so I use different names for many of the sgnals. Anyway....
The display enable flip-flop is set by the logical AND of 2 signals. One, you call EOW and I call IOcmd(13) (because it's the active high version of the I/O command decoder, the '154 on the clock board). The other you call Q3 and I call Q(3). This is bit 3 of the Q register.
Now, Q(3) doesn't tell us much. The Q register (Qualifier == machine instruction) is a shift register in the CPU, and data is being shifted through it during every instruction execution. Therefore I'd expect the various bits to be changing.
However, EOW (IOcmd(13)) is more interesting. It should only go high during an I/O operation. If it is going high sometimes, it means the CPU is executing some I/O operations.
As an aside, HP claimed a separate I/O processor at one point. I think it's fairer to call it a state machine. I/O operations put the main CPU microcode into a tight look, and a latch on the clock card is loaded from some of the bits of the Q register (machine instruction, these bits define what sort of I/O operation is to be performed), then it cycles through a few states. The output of this latch feeds the '154 I mentioned.
As to the clock pulses. There are 2 main clocks in the 9810. The bitclock is the 8MHz master clock and is used to clock bits through shift registers, etc. It's divided down by a counter ('193? '163?) on the clock card to produce the microcode clock. This counter is controlled by 4 bits of the current microinstruction. What this means is you can have between 1 and 16 bitclocks for every microcode clock. This is used, of course, to do the same operation on several bits of the same register (it's bit-serial, remember).
My next test would be to see if it's reading memory (look for a '155 decoder that decodes the R field of the microcode word, I think it's outputs 3 and 6 you want to look at -- this chip is on the -66513 board towards the bottom left corner). If it is reading memory, then see where -- grab the outputs of the M register (these are on the memory box test connector -- I can dig out the pinout). If possible, look at the T register (the other side of the test connector) a few cycles later to see what it's read.
Another idea would be to trigger on the EOW signal (my
IOcmd(13) and see what the bottom 5 bits of the Q register are doing (Q(0) .. Q(4)). These are the select signals (1-of-n code) for the various I/O devices. It would be interesting to see what it thinks it's accessing.
Finally, the optional memory board. In the memory box (the metal box at the left side of the machine) are 6 PCBs. From the bottom they are :
Firmware ROM card,
Memory control,
Memory address (M register is on this card),
Memory data (T register is here),
Standard RAM,
Optional RAM.
You can remove the top card (IIRC red and blue handles). The other boards must be in place.