What's the digital thing in my computer - looks like a clock

Question

My computer was custom built. There's this little thing inside I can see (the tower's left side is clear plastic). It looks like digital clocks, only with two digits. It seems like it may have been a thermometer or something, since it only has 2 digits. Can anyone confirm this? I'm asking because today my computer has been freezing nearly after logging in (probably takes 120 seconds) and that little reader I was talking about says "FF" instead of numbers like normal.

Any ideas what this piece of hardware is, or what "FF" would mean?

EDIT: Actually, I just realized I think it's probably reading hexadecimal, since at one point it said "7F".

Answer 1

Like JRobert mentioned, some motherboard are equipped with 2 digit hexadecimal diagnostic displays. Typically on these, 'FF' is reserved as the last message, which indicates that all the other tests have completed. This doesn't really indicated whether there is a problem or not.

What you need to look for is anything displayed prior to the FF.

This may not be correct for you, depending on the manufacturer of your motherboard. I would pop open the case and see if you can identify the company, and model of that particular board. Then check their website, and download the manual for it, you should be able to get more detailed diagnostic information from them

Answer 2

FF is Hexidecimal for 255, which in binary is almost the highest number in 8bit systems (i.e. 2^8 = 256). It probably means max value.

If it is a thermometer, you have a problem. Is there no documentation that came with the PC, or you never asked what the display indicated?

Answer 3

Some boards were built with a digital readout that the BIOS could use to show error codes, in case the power-on self-test fails with no way to write to the screen. Perhaps your custom board has one of those.