1 Mar
2008
1 Mar
'08
9:44 p.m.
From: "Chuck Guzis":
I'm curious why anyone would want a front panel
with lights and
switches. Except for some early IBM mainframe stuff, the number of
systems that I've worked with that had no front panel vastly
outnumber the ones that did.
Indeed, the front panel on the MITS 8800 seemed to be a waste of good
components and an anachronism at that. Better to take the costs of
the panel and roll them into a good diagnostic ROM with loader. The
S-100 followup machine that I used, an Integrand box, had only a
reset button on the front panel. I never missed the switches. After
the MITS box, I never owned another system with a blinkenlights-and-
switches front panel.
Just trying to understand.
I think of blinkenlights as way ahead of a ROM with a debugger in it,
and not for just the aesthetic reasons folks are talking about. It's
a little like Tony's fondness for "things he can understand". When I
use a front panel, there's no question what's going on in the hardware
or what's in the register. The front panel is such a simple device
there is no way for it to lie to me. No way is it going to miss my
breakpoint and wander into the weeds, etc. I'm not acting through
an intermediary -- I really am in control of the machine, and I'm
seeing the real machine state.
Later, this got stretched a bit. The actual workings of an IMSAI
front panel leave some potential for strange things to happen, as
what going on there is a little like a debugger activated by switches.
At least you can really stop the machine, etc.
Some of the 7-segment front panels with the microprocessor in them
are stretching the point, too. There's a lot that can go wonky in
those, that will make it look like things are going on in the CPU
that aren't. But the classic wall-of-switches and lights was wired
into the machine directly, and couldn't lie to you if it wanted to
(except for the occasional burned out incandescent bulb :-)).
I do use debuggers in core, of course, but I percieve that as a
trade of ease-of-use vs knowing what's really going on.
Vince