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There are some keyboard combinations that will result in the keystrokes not being detected.

One that happens to me daily (as I often need to write an all-case CENTER), is RIGHT-SHIFT + C + E. Try it: press right shift, hold it, press c, hold it, press e, hold: you will notice that, instead of "CE" (or "CEEEEEEEEEE"...), you will get "C", or more likely "CCCCCCCCCCCCCC...."

Several other combinations are likewise impossible; RIGHT-SHIFT + A + S + Q, is another that comes to mind, as it is common in games.

A common key mapping is ASDW for movement(left-back-right-forward), and hold shift for running, so if you want to run sideways and back (SHIFT-A-S) and at the same time perform a Q action of some kind, there is no way to do that other than changing your bindings.

Does anybody know if this is a hardware or software limitation?

Seems like a hardware limit to me, but then, is it possible that the same "faulty" circuitry is used by (basically) every single keyboard manufacturer on the planet?

Is there a keyboard that can actually have all 100+ keys (or at least any 10-key combination, seeing how the average human only has 10 fingers) pressed at once, and detect and send them all correctly to the OS?

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closed as not a real question by Linker3000, David, studiohack Aug 1 '11 at 1:07

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RIGHT-SHIFT + C + E worked for me... –  David Jul 7 '11 at 15:36
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@David it is dependent on the make, model, and revision of your keyboard. Unless you have the exact same keyboard as Asterix, then you will most likely have different key groupings for which key combinations work or don't work. –  Darth Android Jul 7 '11 at 15:58
    
I'm curious why you need to hold all those down. . . I works fine for me. Or I just hit Capslock. –  surfasb Jul 7 '11 at 17:21
    
games require that kind of crazy key combos. some time ago, I played a lot games with 2 players in keyboard :p so wsad+some other letter keys for 1st player "joystick" and arrows+number keys or other letter keys for 2nd player "joystick" (normally Liero game), and sometimes the speaker were so noisy or in game it "moved alone" or did not do nothing :) –  kokbira Jul 7 '11 at 18:13
    
the maximum was playing 4 persons in a keyboard, hahaha –  kokbira Jul 7 '11 at 18:14

3 Answers 3

up vote 10 down vote accepted

Often this is a hardware limitation, known as Key Blocking. To simplify the internal wiring of the keyboard, many keyboards divide the keys into groups, and can only detect two simultaneous keypresses within that group. Higher-quality keyboards have more groups and can detect more simultaneous keys being pressed. Usually, Ctrl, Shift and Alt are in their own groups (since they are often pressed in combination with other keys), and on quality gaming keyboards each of WASD are often in a separate groups. The arrow keys are often in separate groups as well. There's usually no real way to figure this out short of manual testing, though you might be able to find a review online of someone that has already mapped out the key groups.

It's not that the circuitry is "faulty", it's that having a dedicated data line for all 100+ keys would require a lot of additional hardware when it's usually rather rare to encounter the issue. Why only two keys per group? Because with key-matrix keyboards (pretty much every keyboard that we have today), pressing three keys at once causes a fourth "phantom" key to be detected. So the solution to this was simply ignore any keys after the first two pressed in a key group.

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Here ( dribin.org/dave/keyboard/one_html ) is a pretty good breakdown of the subject. With pictures –  horatio Jul 7 '11 at 17:17

It's a hardware limitation. And no one manufactures true multipress keyboards any more; you'll have to find a used Northgate Omnikey or Avant Stellar.

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Multipress seemed to be a good google keyword, and it did bring up a couple of interesting hits... Alas, while both multipress and multitap seem to be favorite topics for cell phone keyboards, nobody seems to care much about PC keyboards. If you want to test your keyboard, try this: –  Asterix Jul 10 '11 at 6:35
    
-1 for no one manufactures true multipress keyboards any more - that is blatently untrue. Just search for an NKRO keyboard - my keyboard can sense every key being pressed at once. –  BlueRaja Feb 3 '12 at 1:23

Thanks to Darth Android for the exhaustive reply and Ignacio for a good google keyword (multipress), which generated a number of useful hits. Both multipress and multitap seem to be favorite topics for cell phone keyboards; alas, not many people seem to care much about PC keyboards.

This page provides a comparison of a few logitech keyboards:

Logitech Keyblocking

I could find plenty of explanations (once I had a good keyword) but, strangely enough, no list of "gaming" keyboards and their limits. You'd think that would be a marketing point, seeing how this problem is so very common in games?

For those who want to test their keyboard (but don't want to download a specific software), this page shows which keys are detected as being pressed together at any time:

Keyboard Woes

For those who want to make their own keyboard, extremetech has an article on how to hack your keyboard, including a list of commercial encoders. Be warned though, the best commercial encoder in the list (140$) only supports 72 inputs. That's less than your average laptop keyboard, which has over 80 keys. Overkill for gaming, sure, but not so much for typing...

Note that that is 72 direct, completely separate inputs. 72 keys that can all be pressed and released in any order, and still be recognized no matter how many are already pressed. Cheaper matrix encoders, also in the list, can be used to make a full layout keyboard, just like a commercial one, but just like with a commercial keyboard you will run in the same blocking problem described both in the other answers and the linked pages.

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The term you want to google is NKRO. You can find a half-decent NKRO keyboard for around $50, but as long as you're going to splurge on a keyboard, you might as well spent an extra $50 and get a keyboard that's mechanical as well. Mechanical keyboards are expensive, but they last forever. –  BlueRaja Feb 3 '12 at 1:25

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