28 Dec
2005
28 Dec
'05
5:38 p.m.
I've used the Digiikey service to get a custom frequency (20.2752MHz,
4x the 5.0688MHz clock frequency of a DL11-W). A little pricey (~$8
each), but worked just as expected.
For your application though anything in the 25-27MHz should work just
fine. If you are really adventurous put in a socket and get a few
frequencies up to 33MHz or so and see how fast you can really go.
Clock chipping an oscillator based PDP-11 is a lot more
straightforward than an older tapped delay line design like a 34, 44,
etc.
On Dec 28, 2005, at 4:35 PM, J.C. Wren wrote:
You can order oscillators programmed with custom
frequencies
from DigiKey, assuming you're speaking of oscillators and not a
crystal (I have someone at work who routinely interchanges the
terms, and it drives me up the wall). They may not be in metal
cans, but they are available in the same foot print. DigiKey can
have them to you as fast as you want to pay for shipping.
--jc
Charles wrote:
> 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.
>
> thanks
> Charles
>
>