Use a POST card from userspace

Okay. This time my small server got screwed up. Totally. segfaults at no apparent reason, lags, and finally the PC not starting at all. Since ssh was down, I had to debug using a UART and a POST card (No monitor in the closet where it stands usually). In the end I had to take the small thing out of its place to the table. A detailed analysis showed up that it was the RAM. Luckily I had a spare 2 GiB chip around and popped it in. However, while troubleshooting it, I hooked the POST card…
The last thing gave me an idea. Not sure if that was done before.

Theory:
The POST card shows data from 80h adress where BIOS stuff writes the codes. Once the system has booted, BIOS doesn’t touch it.
Question:
Can the userspace software write something there?
Implementation:
I didn’t see any reasons why no, so while the backups were untarring to the HDD, I quickly threw a small piece of software (github link).
And it worked awesomely. Obligatory video:

What i got is a small utility to control a POST card from userspace. Basically, I can now troubleshoot bootscripts, and whatever stuff I want using a POST card. Not sure it has a big practical purpose, but it was still fun enough.

Print Friendly

One thought on “Use a POST card from userspace”

  1. You could use for GPIO output on any standard PC, got a nice 8bit bus there you could use to drive a heap of devices.

Leave a Reply