After my lower memory slot failed, it took me quite some time to realize it. While the Mac does a Power On Self-Test of certain hardware, it gave me no notification that this slot had failed. It is possible to get to a report in System Profiler, but only if you launch the application and check it.
There is a command-line version of the System Profiler application called system_profiler. This utility takes optional data types as parameters, such as the the SPDiagnosticsDataType. I put this utility in a super-short Apple Script:
set post to do shell script¬
"/usr/sbin/system_profiler SPDiagnosticsDataType"
if post does not contain "Result: Passed" then
display dialog post buttons {"OK"} with title "Error"¬
with icon stop
end if
I then set this Apple Script as a Login Item and if everything goes well, I'll never see it. However, if the phrase 'Result: Passed' does not appear in the Power On Self-Test, a dialog will appear indicating what went wrong.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2006041909392091