[geeks] new keyboard goodness

[nate at portents.com]

On Tue, 19 Apr 2011 21:35:42 +0100, Mike Meredith <very at zonky.org> wrote:
> On Tue, 19 Apr 2011 08:25:05 -0400, Shannon wrote:
>> The only difference is that USB can only support 6 keys, so that mode
>> is usually called 6KRO.
> 
> Interestingly enough this may be an urban legend propagated by lazy
> keyboard manufacturers. Judging by comments made in Another Place,
> people who have built their own USB keyboard controllers can get more
> than 6-kro with the right o/s drivers (Linux and Windows from memory).
> It seems that the 6-kro limit is supposed to apply just to pre-o/s
> environments.

I think you're referring to the fact that HID has a keyboard basic
fallback mode for BIOS compatibility that all keyboards have to adhere to
(where the 6KRO comes from), and that the HID spec allows larger packets
that have more data in them, but that it's rarely used, and this lack of
use has caused 6KRO to become prevalent in USB keyboards.

If I'm remembering correctly, the Microsoft SideWinder X4 keyboard (a
rather unremarkable membrane keyswitch gaming keyboard) can achieve a >6KRO
over USB by sending HID packets that have more data in them, in combination
with an additional USB driver that can interpret those packets.  The other
method of achieving >6KRO over USB is how the Noppoo Choc Mini does it, by
creating multiple virtual 6KRO HID devices, however while that doesn't need
an extra driver, it doesn't work well with all operating systems (and
doesn't work at all with OS X).

- Nate