What is checked during POST?

The Power On Self Test process performs a series of hardware diagnostics before the operating system loads. Which of these problems would NOT be found during POST?

A) A missing CPU heat sink

B) A faulty video card

C) A bad RAM module

D) A bad hard drive

The answer: A) A missing CPU heat sink

A heat sink’s job is to redistribute the heat from a hot CPU into the heat sink, where it’s then cooled by the constant airflow through the computer case. If the heat sink is missing or isn’t connected well, you won’t know there’s a problem until the CPU heats up.

The incorrect answers:

B) A faulty video card
Bad video cards can be a problem, since no video means you have no visual feedback on the boot process. For bad video cards, the BIOS often beeps to inform you of the bad video.

C) A bad RAM module
Since nearly everything on your computer uses the RAM, those chips are given a good once-over during the POST process.

D) A bad hard drive
When a hard drive goes missing, it’s an easy thing to identify. If a drive is missing or won’t respond, the BIOS will complain.

Want to know more? Watch “BIOS and CMOS Overview.”

What really happens when you start your computer? In this video, we’ll show you how the BIOS handles the most basic operations of your personal computer and how the CMOS stores all of your important configuration information. We’ll also show you how to use VMware Player or Microsoft Virtual PC to create a test lab on your computer where you can test BIOS changes without modifying your PC settings.

4 thoughts on “What is checked during POST?”

  1. Actually, I would have answered it as A a few months ago, but my POST actually let me know that my cooler/fan that I did have on my computer was not cooling down my CPU enough. It wasn’t until I got a better cooler/fan when the error message went away. I could get in still by press the F1 key, but was warned about that issue.

  2. This one is pretty obvious to me. O_o

    How on Earth will a circuit, no matter how sophisticated, be able to detect something that isn’t electronic, such as a heat sink, especially when considering that they don’t directly connect?

    You can say that a lack of a heat sink or fan, due to the absence of a fan, can be inferred by the user AFTER the POST has ended abruptly due to CPU shutting down, but not “during” (as specifically mentioned in the question) POST.

    In that sense, the question could be deemed a bit tricky. I guess one should avoid “thinking too hard”. These test questions were probably meant to be straightforward rather than tricky.

    1. Kevin –

      This question was designed to relatively straightforward if you’re familiar with the POST process and the diagnostics that it performs. If you know about POST, you probably knew the answer right away.

      The previous comment related a POST error to a malfunctioning fan, which is certainly within the capabilities of the POST diagnostics.

      I always avoid “trick” questions, as the CompTIA A+ exam is very clear about its questions and possible answers.

  3. “Actually, I would have answered it as A a few months ago, but my POST actually let me know that my cooler/fan that I did have on my computer was not cooling down my CPU enough”

    That’s not the same as a missing heat sink.

    the Professor is, of course, correct: If you know what POST performs, the “heat sink” jumps right out.

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