Your motherboard still has “useless” headers from the 1990s, and licensing agreements are to blame

If you take a long, hard look at your motherboard, you'll notice that it comes with some legacy ports on them, such as Serial (COM), Parallel (LPT), and PS/2 headers. It can be really tempting to assume they're there because the motherboard companies are lazy, but in fact, there's a good reason they're there. And the answer lies about three decades ago.

The story starts with a bid to get rid of legacy hardware

It was a way to help cut down the number of pins used

The story starts back in the 90s, when Intel announced the Low Pin Count (LPC) interface. It wanted to get rid of the Industry Standard Architecture (ISA) bus, which used a lot more pins than LPC did (hence, 'Low Pin Count'). However, Intel had a problem: how would it get manufacturers to adopt this new tech?

Fortunately for it, it had a plan. Jan Camps, marketing manager for Intel's Platform Component Division, said at the time:

"As the industry moves toward more powerful, higher bandwidth solutions, it becomes a burden to carry the older, legacy technologies because of the higher pin counts which require more space, cost and testing procedures. Through our R&D efforts, we have found a way to facilitate this migration, which will result in lower costs and improved efficiency for hardware OEMs and developers, and make the benefits of higher performing technologies available more quickly for PC users. Intel has opened the specification so the industry can quickly adopt the technology and integrate it into motherboard legacy I/O peripheral development."

Take special note of what Camps said in that last line. He said that the specification was open to the industry, and this was the main draw Intel used to get people to actually use this new hardware. Companies could use LPC as a royalty-free tech, and with the rapid adoption, Intel could facilitate the move over from ISA much faster.

The royalty-free tech saw lots of adoption amongst manufacturers

It helped Super I/O controllers find a new home

So, manufacturing companies did just that; adopt it. Companies such as Nuvoton, ITE, and Winbond found that LPC was a highly efficient bus for their existing Super I/O chip. These chips are still in our computers, with support for legacy devices such as Serial (COM), Parallel (LPT), PS/2, and floppy drives. Manufacturers also used the Super I/O chip to monitor vital computer variables, such as reading thermal sensors to see how hot the hardware was getting, and controlling the fan speed.

TPM 1.2 stepped in to give the hardware yet another use

Why reinvent the wheel?

Fast forward to the early 2000s, and the LPC bus has been widely forgotten about apart from legacy peripheral use. It still hung around because it cost very little to include, and because the technology was royalty-free anyway.

The Trusted Computing Group saw potential in this bus. It could use the LPC bus to power its new TPM 1.2 chip, a cryptographic coprocessor. After all, all motherboards had one by standard, the TPM 1.2 chip didn't require a ton of bandwidth to work, and the LPC bus didn't consume too many pins.

So, they connected the TPM 1.2 chip to the LPC bus, and that's where the technology 'lived' for a while. The bus itself was royalty-free, after all, so they didn't need to pay anything extra to use it, nor did they have to worry about any licensing. Eventually, TPM 1.2 fell out of favour when it was discovered it sent everything in unencrypted text, meaning someone with physical access to the PC can use logic analyzers to grab the decryption keys as they were being sent.

There's not much reason to get rid of the hardware, though

It doesn't cost a lot to keep them around

So, this technology has been around for decades now. It's baked into the design, and people still use them today, if only to keep their legacy hardware going.

Every modern-day PC still relies on the Super I/O chip, which handles tasks like fan speed control, keeping tabs on temperature sensors, and keeping the voltage ticking over. All the logic for these "useless" headers is still sitting within the Super I/O chip, and figuring out a way to remove the functionality would cost more than just sticking a plastic pin header on it. Plus, there's no real incentive to get rid of the support.

Manufacturers can keep support for them, with zero additional cost, no concerns about breaking legacy DRM tools, and not working out how to strip the headers from the motherboard for no reason other than "People don't really use them as much as they used to." So, they stayed.