Pci/usb post boot test/analyzer card

I apparently can't diagnose a bad motherboard myself unless the last computer I diagnosed I didnt reset BIOS completely. Is taking out the power cord and holding the power button for 30 seconds enough or does battery need to be removed? If so for how long?

My main question though is about these cards
id like something to analyze what peice of hardware is broken

would they clearl diagnose a bad motherboard? what a bout processor?

would it be as simple as just checking the code and read "bad motherboard" next to it?

any downside to these cheap $10 dollar ones I see on ebay?
are usb ones just as good? which analyzers would work in all or almost ALL computers besides USB?

thanks so much everyone.

 

A few years ago, I bought 2 different ones from the bay and they were both worthless.

I'm sure that there is something out there that actually works, but you probably get what you pay for.

 

To reset a BIOS correctly either the battery needs to be removed or if a special BIOS reset button is provided that needs to be pressed according to the manufacturer's instructions.

 

damn any other suggestions? i have a pretty big problem diagnosing bad motherboards apparently and never really got anywhere with searching how to. anyone have any luck with these?