VESA cause of "Write-combining range (0x0,0x1000) was already clear"

[Winston]

[xorg-7.5.1, xorg.conf Driver "vesa", Matrox G200eW graphics chip,
 DPMS monitor, DPMS enabled in xorg.conf (and according to Xorg.0.log);
 FreeBSD/amd64 9.0-RELEASE.]

FWIW,

Using the VESA driver, I'm getting about 6MB a day worth of this
message:

(==) VESA(0): Write-combining range (0x0,0x1000) was already clear

in the Xorg.0.log file.  My tests indicate that the event occurs when
the screen blanks (or stays blank), even if the DPMS low power mode is
not activated.  As long as I'm typing and keeping the screen active, I
haven't seen the message get logged.

The message appears to come from X->Xorg itself, not the driver.
However, with the MGA driver, I see similar messages during startup,
but not afterward.

HTH,
 -WBE