Article 117 of comp.sys.cdc:
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From: Kiddo <kent@nettally.com>
Newsgroups: comp.sys.cdc
Subject: More thoughts from the past.
Date: Thu, 22 May 1997 10:13:28 -0400
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After such a long silence, it's good to hear from people that remember
CDC hardware with fondness.  (It's a shame that Control Data's
management wasn't as effective as their iron.)

I've worked a number of sites.  Having been stationed in Tallahassee, FL
for most of my CDC career, I mostly supported FSU.  But I was regional
support and got to a great many other sites.  At one point I knew that
my contributions were running on 5 continents.  :^)

Most sites (understandably) had severe restrictions on the scheduling of
"system's time".  (That time was usually when all users were home asleep
and their jobs were waiting patiently for sunrise.)  Even more limited
was a programmer's access to a system for developing or testing any kind
of I/O drivers.

We solved that problem with a beautiful little simulator.  When it was
fired up, it loaded PPR and waited for interactive input.  It had a full
screen interface that displayed the P-register, A-register, (simulated)
channel status, octal and display values of the direct cells, and most
everything that a programmer sould want to see.  It also allowed you to
set breakpoints based on P-address, and instruction type.  (Breakpoint
on CM read, CM write, PPM read, PPM write, Channel access, Branch,
etc.)  At the breakpoint you could change any PPM value, so CM reads and
writes were implied.  It also had a hook to read CM, but obviously,
writing CM was not supported.

It wasn't the same as a real PP of course, but it allowed considerable
debugging during daylight hours.

Did anyone else build and/or have these kinds of tools?

Kent