thunter0512
Veteran Member
I have been puzzled for a while about the delay of about 1 - 2 seconds in the output of the OS/8 DIR command for larger directories.
This delay is very pronounced when your serial speed is 9600 bps or faster.
Interestingly on my PDP-8/E with AC selected for display you also see some distinct pattern of lights during this delay.
During the delay all AC bits are clear and all address bits are on.
While running from RX01 floppys I never questioned this because I assumed the system was simply reading more directory sectors.
Now I am running OS/8 from an RK05 and the delay still exists.
The hard-sectored RK05 has no interleave, so reading consecutive sectors will have the penalty of about 40 ms (for a full rotational delay).
Of course I wouldn't notice the 40 ms which is insignificant compared to the 1 - 2 seconds delay in the DIR output.
I also noted that the read light on the RK05 is off during this 1 - 2 second delay.
This delay exists when running OS/8 on SIMH (PiDP-8/i), the SBC6120 and a real PDP-8/e.
Does anyone have an explanation for this little mystery?
Thanks
Tom
This delay is very pronounced when your serial speed is 9600 bps or faster.
Interestingly on my PDP-8/E with AC selected for display you also see some distinct pattern of lights during this delay.
During the delay all AC bits are clear and all address bits are on.
While running from RX01 floppys I never questioned this because I assumed the system was simply reading more directory sectors.
Now I am running OS/8 from an RK05 and the delay still exists.
The hard-sectored RK05 has no interleave, so reading consecutive sectors will have the penalty of about 40 ms (for a full rotational delay).
Of course I wouldn't notice the 40 ms which is insignificant compared to the 1 - 2 seconds delay in the DIR output.
I also noted that the read light on the RK05 is off during this 1 - 2 second delay.
This delay exists when running OS/8 on SIMH (PiDP-8/i), the SBC6120 and a real PDP-8/e.
Does anyone have an explanation for this little mystery?
Thanks
Tom