Talk:Rollover (key)

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Wikified as part of the Wikification wikiproject! JubalHarshaw 14:11, 26 October 2006 (UTC)

Rewrite or merge[edit]

This page is in desperate need of a rewrite or possibly a merge with Keyboard matrix (Music). When I got here the information about 3-key rollover was completely wrong; 3-key rollover is an example of jamming (and ghosting; jamming is just a method to prevent ghosting) which is a direct result of how the keyboard matrix works; it doesn't happen on keyboards without matrix. Looking at the circuitry of the matrix it's also easy to see that a keyboard that lets you use any 3 key combination but not 4 key combinations doesn't actually exist. (talk) 14:39, 11 October 2008 (UTC)

“Key rollover” in X.509 Public Key Infrastructure[edit]

The term “key rollover” (which redirects to this article) is also used in context of Internet X.509 Public Key Infrastructure, see RFC 5280. This should be referenced in this article with a link in a box at the top, or a disambiguation page should be added, or the redirect should be changed/replaced with an own article about the key rollover procedure in the Internet X.509 PKI. – (talk) 22:07, 14 January 2010 (UTC)


Kallage, R. (1972). Electronic keyboard design with n-key rollover. --Mgenerous (talk) 00:21, 8 June 2010 (UTC)

Rollover on USB 3.0[edit]

Someone needs to figure out, if N-key Rollover, is possible with USB 3.0. I have not been able to find any conclusive evidence. Mr FJ (talk) 15:34, 24 August 2011 (UTC)

I don't see why not. Even USB 1.0 in 1.5 Mbit/s Low Speed Mode has the bandwidth to handle 1.5*10^6/128 = 11,700 updates per second with 128-key rollover, if the keyboard supports it. Even if you're using a super fancy/expensive monitor that updates at 120 Hz instead of 60 Hz, that's enough bandwidth to update your keyboard almost 100 times for every time your screen updates. The point is N-key rollover does not depend on which version of USB you use. It depends on the quality of your keyboard. (talk) 06:20, 22 April 2015 (UTC)
I came across this Reddit thread discussing key rollover on USB. Apparently USB uses 7-byte packets and its HID protocols (used for generic keyboard drivers) restrict each moment of input to use a single packet, limiting normal USB keyboards to only 6-key rollover. However, it's also possible for keyboards to emulate USB hubs and pretend to be several keyboards at once, with each virtual keyboard providing some of the keys and the OS merging the key events from several keyboards it sees into a single key input stream. I imagine that this requires several times more processing power and USB bandwidth use than a "proper" N-KRO keyboard and driver, but it's apparently the only universally compatible way to do it. So my calculations above (I'm ""), though accurate in terms of raw bandwidth, might not prove USB 1.0 to be capable of N-KRO, at least not without custom drivers to use 2+ USB packets per input frame (2 packets * 7 bytes/packet * 8 bits/byte = 112 bits: enough for 10X-key keyboards). USB 3.0, however, almost certainly provides enough power and bandwidth for an N-KRO keyboard to do a bunch of extra processing and split the key stream into, say, 18 emulated keyboards. I'm not sure if I'm more horrified by how crazy a hack is required for USB N-KRO to work or more awed at so much inefficiency seems practical enough that it wouldn't even be noticed by most users. MarkGyver (talk) 11:20, 28 January 2016 (UTC)

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