xdm & syscons failing to get along ... sometimes?

I've been tracking RELENG_6 (on slice 1) and HEAD (on slice 4) of
my laptop (currently a Dell Inspiron 8200) for a while now.  And
while I've been fairly pleased with the overall behavior for both,
there's one issue that shows up a lot more often in CURRENT than
6.x, and it's getting to the point where I'm about to start poking
around to try to figure out what's going on so I can fix it.

But before I do, I thought it might make sense to describe what I'm
seeing & ask if other folks are seeing it or if other folks are trying
to fix it (so I can work with them, vs. at cross-purposes).

Briefly:

* I start xdm via a script in /usr/local/etc/rc.d.

* In the past (since FreeBSD 2.2.x or so), this has worked without any
  problems at all.

* More recently, sometimes after the machine boots, the virtual terminals
  provided by syscons(4) don't seem to work.  Symptoms include:
  * Typing my login on the xdm login screen fails to echo, but the
    information does appear to be read by getty(8). 
  * Indeed; I am actually able to login, though seeing that is almost
    impossible, because the various Ctl+Alt+Fx chords don't show any
    vtys, either.  But after I enter my login & password, I can (blindly)
    type "sudo reboot" followed by my password, and the machine then
    reboots (if I typed everything correctly).  Thus, it appears that
    there's a bit of a "disconnect" between what process is actually
    accepting keyboard input vs. what process is controlling the display.

* I have tried tinkering with the rcorder(8) keywords, as well as
  creating an additional "startup script," the job of which is to
  insert a "sleep" before xdm starts up.  Although I've been able
  to make the symptoms rarer, I have not been able to make them
  stop completely.  I tweaked that extra script to add more delay for
  7.x; that seems to help somewhat, but even adding 12 more seconds
  doesn't prevent the problem from recurring.

* Usually a reboot does not exhibit the same symptoms.  Sometimes, it does.

* As noted above, it's more common in 7.x than in 6.x.  I don't recall
  ever seeing the problem in 4.x or earlier.  (I didn't spend enough
  time running 5.x to recall.)

* I have not seen the problem on my desktop at work, where I also
  track RELENG_6 & HEAD, and also run xdm via a script in
  /usr/local/etc/rc.d.

As noted, the laptop is a Dell Inspiron 8200; here's some salient info
about the hardware, taken from dmesg:

FreeBSD 7.0-CURRENT #47: Thu Apr 13 10:14:06 PDT 2006
    root_at_localhost:/common/S4/obj/usr/src/sys/LAPTOP_30W
...
Calibrating clock(s) ... i8254 clock: 1193216 Hz
CLK_USE_I8254_CALIBRATION not specified - using default frequency
Timecounter "i8254" frequency 1193182 Hz quality 0
Calibrating TSC clock ... TSC clock: 1594832736 Hz
CPU: Intel(R) Pentium(R) 4 Mobile CPU 1.60GHz (1594.83-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf24  Stepping = 4
  Features=0x3febf9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM>

Instruction TLB: 4 KB, 2 MB or 4 MB pages, fully associative, 64 entries
Data TLB: 4 KB or 4 MB pages, fully associative, 64 entries
1st-level data cache: 8 KB, 4-way set associative, sectored cache, 64 byte line size
Trace cache: 12K-uops, 8-way set associative
2nd-level cache: 512 KB, 8-way set associative, sectored cache, 64 byte line size
real memory  = 268312576 (255 MB)
...

/var/log/Xorg.0.log tells me the video card is a "nVidia Corporation
NV11 [GeForce2 Go] rev 178;" I'm using the X.org "nv" driver.


My current work desktop is a Dell Dimension 3000; its video card is
shown as "Intel Corporation 82865G Integrated Graphics Controller rev
2;" I'm using the X.org "i810" driver.

Here's a corresponding exerpt from dmsg.run (running 6.x):

FreeBSD 6.1-RC #41: Sun Apr  9 06:21:31 PDT 2006
    root_at_localhost:/common/S2/obj/usr/src/sys/CATMINT
ACPI APIC Table: <DELL   3000   >
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (2793.01-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf41  Stepping = 1
  Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,C
MOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0x441d<SSE3,RSVD2,MON,DS_CPL,CNTX-ID,<b14>>
real memory  = 535232512 (510 MB)
avail memory = 514396160 (490 MB)

Hints, pointers, suggestions, or fixes would be welcomoe.

Peace,
david
-- 
David H. Wolfskill				david_at_catwhisker.org
Mail filters, like sewers, need to be most restrictive at the point of entry.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.