[vox-tech] XF86Config Question

[Rick Moen]

Quoting Peter Jay Salzman (p at dirac.org):

> A while ago, Rick Moen posted that any modern monitor has protection
> circuitry that prevents you from driving the CRT at frequencies that would
> damage it.   Certainly makes sense to me that a monitor would be engineered
> that way.

Near as I can figure it, the lingering warnings about damaging one's monitor
by sending it a video signal it can't handle are a holdover from a
"stepwise disaster"[1] that occurred in the 1980s.  

Early VGA monitors were fixed-frequency -- which was immediately
extended by the Video Electronics Standards Association and others to a
limited, known _set_ of fixed frequencies.  It wasn't (at first)
anticipated that people would experiment with input frequencies
("detent" settings), so early production units had no protection
circuitry.  This was apparently also the case with some of the first
generation of auto-synchronising monitors, pioneered by the NEC
MultiSync.

If you sent such a monitor a signal just barely outside its
ability to synchronise, it would strain to manage the feat, anyway --
and you could hear a high-pitched whine as it made the effort.  That
whine was a warning sign:  If you dove for the power switch within the
first couple of minutes, the monitor would be OK.  Otherwise, boat
anchor.

Immediately following those early production runs, all monitors I'm
aware of simply detect arriving input signals outside the supported
range of frequencies, and blank the monitor harmlessly until the signal
changes to one inside the supported range.

Word has it that LCD (as opposed to tube) monitors were/are for some
reason always immune to the strain-unto-death syndrome.

Boilerplate instructions for video setup (e.g., for X11) still tend to
carry dire warnings about possible monitor damage because nobody wants
to get hatemail from the one-in-a-million owner of an antique monitor 
(or some offbrand unit inexplicably lacking protection circuitry) who 
watched his pride and joy spew its magic smoke.

> Also, don't forget about "XFree86 -configure".  This will get you in the
> right ballpark.  After writing a reasonable XF86Config-4 file, you can fine
> tune your way to the front row seats.

Running that (as you say, while one is the root user) and then examining
/var/log/XFree86.0.log is usually enlightening.

-- 
Cheers,             $n=99;sub b{"$n bottle${[s=>]}[$n==1] of beer"}
Rick Moen           print$b=b, $w=' on the wall',
rick at linuxmafia.com ",$b! Take one down, pass it around, ",b($n--),"$w! "while$n
                                                -- Ben Okopnik