30 May
2013
30 May
'13
10:53 a.m.
On May 30, 2013, at 11:41 AM, Dave McGuire <mcguire at neurotica.com> wrote:
On 05/30/2013 07:32 AM, allison wrote:
Yeah, the thing with at least the 11/23 is that most of the board runs on
a common base clock, including the QBUS logic. There's no separate clock
domain for that. So if you're ramping up the speed of the CPU, you're
also cutting down on your timing for QBUS, and the 11/23, slow as it is,
is timed pretty close to the QBUS minimums already. There's not a lot of
room before you start violating setup/hold timings for the other boards
in the system (which is essentially what Allison said).
- Dave
That said I've pushed the clock on 11/23
board once too see and the 13mhz
clock was wound up to 25mhz using a external source. I started seeing
errors above 18mhz but they were random, seems bus timing and memory
timing all had to be happy and I was pushing the margins. I eventually
put in a clock module for 15.8mhz as I had one. For that it was a modest
speed up as the 11/23 is slower to start with.
Hey! I too overclocked an 11/23. My friend Ernie and I were hanging out late one night
hacking on one of his systems, and I had brought a spare 11/23 CPU along for this purpose.
We got it up to 16MHz; we didn't take it any higher than that. I'm amazed to
hear that you got it up to 25MHz!!