How can FreeBSD work with keyboard on a dead southbridge where other systems fail?

[Bernt Hansson]

On 2016-03-25 17:02, Dmitry Bachilo wrote:
> So, here is the story: I have a laptop Acer Aspire 5100, which has a 
> dead southbridge. In any operating system it predictibly results in 
> non-working audio, usb, keyboard and touchpad. I tried Windows XP, 
> Windows 7, Linux and FreeDOS. They all work ok on it except this minor 
> stuff. I also obvioulsy can't access BIOS since keyboard is dead. And 
> if I install FreeBSD on it ofcouse I cant skip that autoboot delay 
> with the boot menu. But if system boots - the keyboards suddenly works 
> like a charm, and that makes my laptop totally usable and fine (for 
> example to set up ethrenet switches using cardbus serial adapter). 
> That's a miracle! Or is it?
>
> So the question is: what makes FreeBSD so different? How does it work 
> with the keyboard and why no other OS uses this method then?
>
> P.S. I even made the video about this situation and it has an image of 
> this laptop's motherboard if needed. Here it is: 
> https://youtu.be/JBt_fbvpGww 

> The question was...