29 Dec
2005
29 Dec
'05
12:17 p.m.
After pulling out my hair for a while trying to get my PDP-11 to
talk to me, I finally discovered that the master clock (26.667 MHz
crystal oscillator) is dead. (KDF-11BA CPU board).
Those metal-package oscillators are very common and inexpensive
(around $2), but I can't find one in that exact frequency. 25,
25.175 and 27 MHz units are available. Semi-custom ones aren't
terribly much more expensive (~ $15) but have longer lead times.
Is there anything in the circuitry that can't be run a little
slower (or 1.2% faster, 27 MHz)? I'm not worried about squeezing
every last MIPS out of it.
I've not actually worked on this machine, but I know that the old Unibus
11's have nothing that depends on the exact freqeucny of the Xtal. I
would be suprised if any of the ones you mentioned wouldn't work fine.
-tony