7 Mar
2015
7 Mar
'15
11:43 p.m.
On Sat, Mar 07, 2015 at 07:38:58PM -0800, Earl Evans wrote:
However, unlike the DEC PSU, the ATX power supply
won't supply a 60 Hz line
time clock (LTC) signal to the backplane via BEVENT. So, my question - has
anyone used a standard ATX PSU for a PDP-11 QBUS system, and if so, how'd
you work around the LTC issue?
I haven't done it with an ATX PS, but years ago I set up a 4-slot
dual-height box (is that BA-11VA?) that didn't drive BEVENT L, to run
RSX11M+ which of course requires the clock, so I dangled a little piece of
perfboard in the backplane (wire-wrapped to BEVENT L and the power pins)
with a PIC CPU that generated the clock. Code here:
ftp://ftp.dbit.com/pub/pic/kw11l.asm
... and there's an ASCII drawing of the ultra-simple circuit in a comment
block there. If I were doing it now I'd use an 8-pin PIC.
John Wilson
D Bit