Time scales of a PDP-11/34 - 200 ms
200 milliseconds - the CPU starts up after Power-ON
In a time window of 0.2 seconds, you see how the CPU begins to run after the reset logic has processed the signals of the power supply:
Relevant signals here are:
ACLO: a High level means "AC line power is unreliable".
DCLO: a High means: The main +5V logic supply voltage is unreliable.
PROCINIT: this signal is inverted, a High means: CPU is held in Reset, CPU clock is stopped.
What you see
- After power is switched ON, all signals are undefined at first. The LA shows them as Low levels.
- At the "T" marker, DCLO and ACLO from the power supply get valid and indicate a "Power failure".
The micro program counter MPC is initialized to 001, which is the start of the power-up micro program.
All other signals show constant nonsense data.
- After Power has stabilized, DCLO goes Low ("A" marker").
- 120 milliseconds later, the PROC INIT signals goes inactive (marker "B").
- The CPU begins to run. You see all other signals begin to oscillate so fast, that no signal traces can be distinguished at 200ms resolution.