| From: Lennart Sorensen via talk <talk@gtalug.org> | On Wed, Mar 28, 2018 at 09:50:42AM -0400, Steve Petrie, P.Eng. via talk wrote: | > *** I know that PS/2 is an ancient interface. I only chose PS/2 because it is my understanding that a PS/2 keyboard and mouse combination is better supported and earlier, during the actual Linux boot process, than a USB keyboard and mouse combination. So PS/2 keyboard and mouse offer more liklihood of functionality when there are Linux boot problems. | | The BIOS emulates PS/2 for USB mouse/keyboard just fine and should | not cause any issues. But yes it is slightly more complex to use a | USB device. I don't remember the last time I dealt with a PS/2 device. | I don't miss them. I don't think I have had a problem with a USB keyboard | for a decade. USB mice are never a problem since you never need a mouse | unless the system is actually booted normally, so only for a keyboard is | PS/2 at all interesting. Well unless you are one of those extreme gamers | that care about the potentially lower latency of PS/2 mice over USB mice. (I may have some of this wrong. These details are considered too complicated to explain to users so we are just supposed to assume everything just works.) - firmware isn't BIOS these days. In fact, that was a misnomer on the PC since day 1. It's a carry over from the CP/M days on Intel 8080 processors. Now it is called, uhh, firmware. Or UEFI firmware. - UEFI firmware usually (but not always) includes a CSM (Compatibility Support Module) to emulate BIOS for the sake of old OSes. If present in the firmware, it usually can be enabled or disabled in the firmware config menus. As far as I know, all stand-alone motherboards have a CSM (Win 10 tablets often do not). - System Management Mode is a little known feature of all Intel and AMD x86 processors since the 486 and the Am486 25 years ago. It allows the firmware to keep some control after booting the OS. The OS has no control over this. - SMM is used (among other things) to capture USB keyboard and mouse events and turn them into simulated PS/2 events. This is usually optional but default behaviour on motherboards. In effect, this emulation appears to be a hardware feature. - One other limitation of USB and not PS/2 is that there is a limit to how many keys can be pressed at once (n-key rollover) and sensed properly. The limit is based on how many key events can be recorded in a single USB packet. But the limit is something like 6. Surely more than enough. So: mouse emulation and BIOS emulation are behind the back of the OS. This means legacy OSes should have no trouble with these features. I recommend using a USB keyboard and mouse. Unless you are a crazy gamer.