Date: Mon, 03 Feb 2003 11:45:50 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Don Bowman <don@sandvine.com> Cc: Attila Nagy <bra@fsn.hu>, Lucky Green <shamrock@cypherpunks.to>, freebsd-current@FreeBSD.ORG Subject: Re: L440gx+ serial BIOS needs text mode Message-ID: <3E3EC6EE.DE9C34F1@mindspring.com> References: <FE045D4D9F7AED4CBFF1B3B813C8533701023645@mail.sandvine.com>
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Don Bowman wrote:
> > Anyway, it was a particular problem with the SuperMicro motherboards
> > with the AMI BIOS that's been the subject of the rest of this
> > discussion (i.e. the ones that kick out the escape sequence at the
> > end, for no good reason, except to screw up non-monochrome VTxxx
> > emulators, and make it hard to use a UNIX box as the serial console).
>
> FYI, I've found that running under 'screen' fixes the problem
> with the odd escape sequences.
> One type of system we have puts out an escape sequence that
> is escape followed by 12 [. Not sure what that is :)
> The other works just great, except it switches to black on
> black just as it switches to the OS :)
I guess we don't get to escape from the gory details... 8-).
The 12 ['s are compressed into a single [, for fully ANSI compliant
state machines, because they are in the wrong column of the old
DEC-published ASCII chart to terminate an escape sequence, so the
real question is "what comes after the last [?". If you are seeing
the 12 ['s, then your ANSI 3.64 state machine is not compliant. 8-).
Back to the color change...
The issue is support for the ISO ESC "[" "3" n "m" and the ISO
ESC "[" "4" n "m" set foreground/set background color sequences.
Windows Telnet doesn't support these, and neither does the
terminal program that comes with Windows by default, but UNIX
consoles do, and so does xterm, so running a dumb tty pipe like
"tip" or "cu" on one of these passes them through. Running "screen"
like you are, the emulation is a dumb VT100, and the escape sequences
are interpreted by the "screen" program, instead of by the terminal
window in which "screen" is running ("screen" is a terminal emulator
that runs in a virtual terminal window, as an implementation detail
for it being able to maintain multiple instances of display memory).
The xterm didn't use to do this, by default, actually, and if you
run your xterm with the "-cm -dc" options, or put:
xterm.colorMode=false
xterm.dynamicColors=false
in your .Xdefaults file. I imagine this change is a result of
some idiot wanting "colorls" to work by default, just as the
BIOS spitting out the sequence was added at the request of
some idiot to give people "one more reason not to use UNIX". 8-).
If it really bothers you, you can disassemble, modify, reassemble,
and then re-flash your BIOS to get rid of it (it bothered me, but
not enough to do that, just enough to make me make an icon that
started xterm with the color disabling arguments, which ran telnet
to the terminal server connected to the serial consoles in the
server room as it's "-e" argument).
-- Terry
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