Re: [MiNT] update:WRITE_BOOT,ALLOW_TRP_CHG

[Paul Wratt <paul.wratt@gmail.com>]

On Sun, Oct 7, 2012 at 7:33 AM, Jo Even Skarstein <joska@online.no> wrote:
> On Sun, 2012-10-07 at 06:10 +1300, Paul Wratt wrote:
>
>> FYI, especially for those considering add that dev to kernel, most
>> (99%) PC keyboards are "cheap" where multi-key-press is concerned, 3
>> is max. only high quality keyboard can register more (read: gaming
>> keyboards) - this then has affect on FireBee, CT6x, and anything else
>> that uses PS/2 keyboards..
>
> This is a myth. There is no limit on the number of concurrent keypresses
> with PS/2 keyboards. True, cheaper keyboards will probably suffer from
> ghosting (pressing three keys will produce a fourth "ghost" keypress
> depending on the key's location) but this has nothing to do with the
> PS/2 protocol. Atari IKBD keyboards suffers from the same problem.
>
> In fact, PS/2 is preferred over USB by "gamers" just for this reason.
> Unlike PS/2, there is a max limit of six concurrent keypresses (plus
> modifier keys) for USB HID keyboards. If you press a seventh key, the
> first one will be lost.
>
> Anyway, this is a limitation of the keyboard and nothing the OS has to
> worry about.
>
> Jo Even
>
you misunderstand post reference. The hardware circuits in 99% of
keyboards can NOT detect/acknowledge more than 3 simultaneous
kepresses (keys pressed at the same time). 4+ keys can be pressed, but
only the first 3 will presented to any interface connection. This is
irrelevant of protocol. This is a side affect of producing low cost
keyboards. You need to know this if your game wants to process
multiple keypress at the same time (eg. diagonal movement + jump +
fire in FPS games = 4 keys), so you will understand why you are ONLY
getting the first 3 keys that an average PC keyboard circuitry passes
on to any OS/driver.

This directly affects the result of any /dev/xkbd driver output, but
not what the driver can process.

Paul