Not a lot of people know this, on most (but not all) retro laptops will output POST codes to the parallel port to help with troubleshooting. To read these codes you will need a parallel port POST card..
So what is a POST code?
The Power On Self Test is a quick self-test that your computer performs each an every time it has been powered on (mainly from a cold boot). It checks things like the RAM, CPU, BIOS and keyboard.
If you are having problems with your computer and it wont load your Operating System you can used a POST card to see what your computer is up to during the POST.
The POST codes you see on a POST card will not tell you what the fault is, what the POST code actually is, is what Test the laptop is currently running.
If your computer wont boot and you put a POST card in and the code it gets stuck on says it's testing the RAM then it is likely that the RAM is faulty so you should start by swapping out the RAM with a known working stick and see if your computer will now POST.
You should get a manual with your POST card as this will help you interpret what the codes mean and they do differ depending on the BIOS manufacturer.
When plugged in to a parallel port you will need to plug the USB lead in to a USB port to provide power to it. If plugged in to a PCI slot on a desktop motherboard then do not plug in the USB lead as it will draw the power from the PCI slot directly.
Once plugged in to the parallel port (and a USB port to power it) all you need to do is power on your laptop and pay attention to the codes that come up on the display.
TOP TIP: If you have a SmartPhone then it's a good idea to record a video as sometimes the codes will change quite rapidly so with a video you can pause it on playback to see what's going on.
This laptop gets stuck with a POST code of 85:
The BIOS manufacturer is American Megatrends (AMI) so now we need to look the code up in the manual..
IMPORTANT: A POST card will not tell you what is wrong with your computer. What it will tell you is what test is being run. This laptop has stopped with a POST code of 85:
Low and behold the CMOS battery is dead so the time isn't set!
The code we all hope to see is FF which means the POST and Boot of the PC has completed and that the Operating System has loaded:
As the POST card that I have also works on a Desktop PC (and not just laptops) there is a 7 Segment Display on the reverse of the card so you don't have to twist your neck around too far to read any codes!
There is also a PC Speaker mounted on the card as some Desktop motherboards don't have one build in:
Just another way of helping you to diagnose your computer.
