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Mac OS X and the missing Power On Self-Test
April 19th, 2006

Recently, the lower memory slot in my 15″ Powerbook decided to break. I think this happened shortly after installing 10.4.5, but I can’t be sure as the machine decided not to inform me of the problem. I did notice a reasonable slow down however but attributed this to the OS upgrade. When I upgraded to 10.4.6 however, I decided, (for reasons I cannot recall) to look at the About this Mac window where, lo and behold, I was informed that I only had 512MB.

After a little investigating I discovered that it wasn’t the RAM I purchased from Mac Mall that stopped working – it was the slot itself. Trying to boot up the machine with only one chip in the lower slot confirmed this. I’ve since had the mother/main/logic board replaced so it’s All Good now. Turns out this is quite a common problem; Apple now have a repair extension program to address this issue.

I’m generally pleased with how Apple handled the issue, what with the very quick turnaround and all, but what am I most displeased with is the total absense of the Power On Self-Test. Before sending in my Powerbook to have its innards replaced, I discovered that if you look under Diagnostics in the System Profiler, there’s a nice little Power On Self-Test (POST) report. At the time, it was quietly telling me that the lower memory slot had failed. It certainly had a very ‘down to the cellar, disused lavatory, beware of the leopard’ feel to it. So what did I decide to do about it? Well fix it of course!

Turns out that there is a shell version of the System Profiler, called system_profiler would you believe. This utility takes optional data types as parameters. One such data type is the SPDiagnosticsDataType. I put this utility to use in a super-short Apple Script:

set post to do shell script

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 voila – assuming 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 telling me what went wrong. If I remove the if statement I can see…

POST dialog

Click here to download the Apple script. Note that the dialog above WILL NOT appear in the downloaded version – only a failing Power On Self-Test will cause a dialog to appear.

  • I hope you posted that onto some apple forums as it seems like it would be quite useful.