- To answer Alien Bob; at the end of upgrading to 12.1, I ran "Xorg -configure" to update the xorg.conf file. This resulted in the intel driver for the 845G chipset being put in the xorg.conf file.
- I tried the VESA driver and found the problem disappeared. However the VESA driver has a lower max. resolution than the Intel driver.
- I found the answer in a Gentoo thread about problems with the i945GM chipset.
- The solution, for my Slackware 12.1 install, is as follows. On a Dell GX260 with Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset:
#####
Step 1:
Add the following "Option ..." lines to the "Device" section of the xorg.conf file
Option "AccelMethod" "EXA",
Option "ExaNoComposite" "false",
Option "MigrationHeuristic" "greedy"
for example (partial xorg.conf):
. . .
Code:
Section "Device"
Option "AccelMethod" "EXA"
Option "ExaNoComposite" "false"
Option "MigrationHeuristic" "greedy"
Identifier "Card0"
Driver "intel"
VendorName "Intel Corporation"
BoardName "82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device"
BusID "PCI:0:2:0"
EndSection
. . .
#####
Step 2:
Create an environmental variable file in /etc/profiles.d/ as file intel.sh:
Code:
#!/bin/sh -
#
export INTEL_BATCH=1
#
# End of intel.sh in /etc/profile.d/
##### Done
I don't know that both steps, or all three options are necessary. However, the listed changes work, and I'm satisfied. Thanks Alien Bob for the input.