I decided to try the x86_64 version of CentOS 5 on my new desktop since it has an Athlon 64 X2 CPU. The one really perplexing oddity is that the monitor no longer goes to power save mode (standby) if the system is idle long enough (e.g., overnight).
The "power management" option is set to put the display to sleep after thirty minutes. The display gets blanked but it never goes to standby. The weird thing is that the display behaved as expected when I still had the 32 bit version of CentOS installed so the hardware supports powering down the monitor.
I don't see anything incriminating in dmesg, /var/log/messages or /var/log/Xorg.0.log. I'll switch the system to boot to runlevel 3 so I can see if X is spewing something to the first alternate console that isn't getting written to the log file. Anyone have other any suggestions as to diagnosing of fixing the problem?
Thanks, Dave