yes it is possible and has been implemented with several keyboards already and there's no any extra delay or anything

which keyboards?

google can help with that

True N-Key is not possible due to limitations with the USB communication interface.

This is a USB limitation, not a keyboard limitation.

USB is limited to 6 "signals" at the same time, which is why n-key keyboards can only do up to 6-key rollover on USB.

PS/2 is capable of n-key, so true n-key keyboards can be used with a PS/2 adapter if full n-key is desired.

Personally I have never needed more than 6-key rollover anyway because I only have 5 digits on my left hand, so I just use my keyboard on USB.

USB keyboards can present themselves as a USB hub with several keyboards attached to get more keys. My ducky g2 pro can do this, but I disable that function and use PS/2 anyway.

The trick they use is to appear as more than one usb keyboard.

Though it's true it truly is unnecessary to have more than "6kro" (including modifiers).

Sorry but I have to disagree.

1, "ok"

2, No, there is no such limitation in the USB standard. (However, Microsoft defined such limitation in the communication interface standard for USB keyboards, and that's why your first point is "acceptable")

3, even old, low speed USB keyboards can transfer 8 bytes in each data packet, so that's 64 keys (that's why they needed special drivers a long time ago, to make two or more virtual keyboards appear as one for the OS)

4, Modern full speed USB keyboards are more than capable of n-keys, no problem. PS/2 is still nice ofc, but also outdated and inferior to USB. The industry doesn’t use the 8255 anymore, and USB is mostly handled by the Southbridge/PCH nowadays (and gets interrupted by the CPU), while PS/2 is handled by some custom I/O chip (and gets interrupted by the device/keyboard).

5, I don't even... :)

No such thing as Southbridge these days, really. Unless you're talking about the Quake crowd, then yes, naturally. =b

Indeed, and I shouldn't have, it was my mistake. Thanks for the heads up, I added /PCH to my post.

I have a keyboard from the Chinese brand "Keycool". It does n-key rollover over USB. To accomplish that, it pretends it is several devices. If I plug it into USB, two keyboards and one mouse show up in the Windows Device Manager. I didn't feel any added delay on USB compared to its PS/2 adapter.

I'd recommend against that sort of keyboard if you don't really need it for some sort of two-handed use or whatever you'd do with full n-key rollover. I can imagine the weird shenanigans it does with those multiple devices leading to problems on some machines, a future Windows version or using it on a Mac.

sneaky chinese keyboard