BIOS POST Card Built Using Raspberry Pi Pico

A computer’s BIOS includes basic diagnostic tools for troubleshooting issues. Often, we rely on the familiar beeps from the POST system for this reason. However, error codes are also available via hardware “POST Cards” that were particularly popular in the 1990s. [Mr. Green] has now built a POST card using readily-available modern hardware.

[Mr. Green] built the device to help troubleshoot an x86 based firewall appliance that was having trouble. Like many x86 systems, it featured a Low Pin Count (LPC) bus which can be used to capture POST troubleshooting codes. By hooking up a Raspberry Pi Pico to the LPC bus on the firewall’s motherboard, it was possible to get it to display the POST error codes on some LEDs. This is of great use in the absence of a conventional PC speaker to sound the error out with beeps.

The build can be used for POST-based troubleshooting on any x86 system with an LPC bus. Files are on Github for those eager to replicate the build. We’ve seen similar work before, too. Video after the break.

18 thoughts on “BIOS POST Card Built Using Raspberry Pi Pico

      1. Who says you have to boot Windows 11?

        People have made Linux distros with recent kernel builds that boot off floppy disks. Getting Windows 11 to boot off multiple disks sounds like it would require far too much modification to Windows to work.

      2. 8” floppy disks generally have a smaller capacity than 5.25”, which in turn store less data than 3.5”. Storage technology improved as the disks got smaller

      3. I can tell you’ve never used an 8″ floppy. They held less than 5.25″, only around 175KB for the first R/W one, rising to 568KB when the first 5.25″ drives were introduced. By the time 3.5″ drives came out 5.25″ floppies could hold 1.2MB. 8″ drives did eventually male it to 1.2MB too but those never made it I to widespread use.

  1. At this point, I’m a little disappointed they don’t have a dedicated UART output (with dedicated headers) that prints POST codes. Seems like it would be easy enough to add to the SuperIO chips.

    1. SuperIO chips usually do have UARTs used for COM ports, though they may not be connected to anything. And even if they are hooked up to something like a DE-9 RS232 connector, the vendor firmware probably doesn’t print anything on it. coreboot (open source firmware alternative) however frequently makes use of any available UART for printing full debug messages. It can even log POST codes to the console. And it’s not just UART, there’s also console options that use USB EHCI debug ports, SMBus, the PC beeper, writing to the SPI flash containing the firmware, and a few others. Oh, and also the normal POST codes over PCI or LPC POST cards.

  2. (Sorry but here’s another.. I remember) … Back in the 90s at work we had an ISA card to diagnose nonbooting/posting motherboards.The first one had just LEDs and a later version had a 7seg display.

  3. Sadly, it seems like some motherboards have been skipping out on this sort of debug info without the adapter – for a few years, most decent boards had it built in.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.