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Whenever I play a PC game with the directional keys, I can only press two buttons at a time. For instance if I am playing a shooter like R-Type, I cannot hold down the fire button while moving diagonally at the same time. The computer simply ignores the extra button press.

How do I remove this limit so I can shoot while moving diagonally? This limitation seems to apply for every game.

I am running Windows 7 if it makes any difference. I noticed the same problem back when I used Windows XP.

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@BlueRaja-DannyPflughoeft Is there a reason you're suggesting the older, higher-voted, and better answered (numerically) question over the newer one? (Just trying to determine if I'm missing something) –  Raven Dreamer Jun 5 '12 at 22:50
    
@Raven: Oh, this question was in the "hot questions" list in the upper-left. I didn't realize it was so old o_O –  BlueRaja - Danny Pflughoeft Jun 6 '12 at 2:51
1  
This does a pretty good job of explaining "keyboard ghosting" as well as a small test of your keyboard's capabilities. –  nevets1219 May 7 '13 at 18:07

8 Answers 8

up vote 44 down vote accepted

This is a hardware limitation of your keyboard. Unfortunately, the only solution is that you must purchase a better keyboard that does not have this limitation.

To be more specific:

In order to save money, keyboard manufacturers often put many keys on the same "circuit" of sorts within the wiring of the keyboard. This prevents multiple keys in the same region of the keyboard from being pressed simultaneously. Sometimes it even prevents more than 2 keys at all from across the whole keyboard being pressed at once. Often the shift, ctrl, and alt keys are not within this limitation, so you can hold shift and press 2 other keys at once and it will still work fine.

Even high-end gaming keyboards often have a similar hardware limitation, although the cap is much higher so that it is unlikely to be reached during the normal course of gaming.

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5  
This is a common limitation of laptop keyboards, especially. –  JavadocMD Aug 31 '10 at 23:43
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Any suggestions on how to identify this when purchasing keyboards? –  Raven Dreamer Aug 31 '10 at 23:59
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Raven > This may sound juvenile, but if you're physically purchasing your keyboard(s) at a store, as opposed to buying online, you could always ask to try it out on a PC, and see how many keys you can press at once. That's what I usually do, and most retailers won't mind. If the retailer doesn't have a computer handy, you could bring a laptop. –  ElfSlice Sep 25 '10 at 21:14
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Notably, Das Keyboard allows 6 keys simultaneously on USB and any number of them on PS/2. –  Joey Mar 7 '11 at 17:08
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@Raven: The term you're looking for is called "Rollover". Most cheaper keyboards are 2KRO (2-key rollover), meaning any two keys can be held down at once and still be detected (though most of them have 3- or 4-key rollover for most of the common key-combinations for games, like keys near W-A-S-D). The maximum possible through USB is 6KRO. Through PS/2 port there is no limit; keyboards which support any number of simultaneous keypresses are called NKRO (n-key rollover). Check the specs when buying a keyboard to find out its rollover. –  BlueRaja - Danny Pflughoeft Jun 5 '12 at 22:23

The keyboard enthusiasts forum at geekhack.org has an extensive list of keyboards (login required) tested for their N-Key-Rollover capabilities, as well as instructions on how to find the number of simultaneous keypresses a certain keyboard supports.

X-key-Rollover (where X is an integer smaller than the number of physical keys) is the minimum number of keys that will register correctly under any circumstances. True N-key-Rollover (NKRO) means that all keys can be held down and register correctly. Most standard keyboards offer only 2KRO, and although it is possible that certain key combinations allow more keys to register simultaneously, this is not guaranteed, and may differ even between different revisions of the same keyboard.

Here's a list of keyboards having a confirmed NKRO over a PS/2 connection or 6KRO/18KRO over USB (which is a USB limitation) from the geekhack.org forum thread (login required) (June 5th, 2012):

Adesso MKB-125B: 6KRO with USB cable adapter, NKRO with PS/2.
Adesso MKB-135B (full sized): 6KRO with USB cable adapter, NKRO with PS/2.
Cherry G80-3494 (Cherry Red): 6KRO with USB, NKRO with PS/2 adapter.
Cherry G80-3600 (Cherry Red): 6KRO with USB, NKRO with PS/2 adapter.
Cherry Corp G80-8200lpdus: NKRO PS/2.
Cherry G80-1950PQAXB.
Cherry Corp MX8100 G80-8113LRCUS-2: NKRO PS/2.
Cherry Corp G80-8113HRBUS-2: NKRO PS/2.
Cherry Ergoplus G80-5000HAMDE/03: NKRO PS/2.
Das S: 6KRO under USB, NKRO with PS/2 purple adapter.
Das 3 (previous model): 12KRO under USB, can not be used with PS/2.
Deck Legend: 6KRO under USB, NKRO under PS/2.
Deck 82 Key: 6KRO under USB (no PS/2 option).
DSI Modular Mac.
Ducky keyboards. 6KRO under USB, NKRO with PS/2 adapter.
Ducky G2 keyboards (special edition). 18KRO USB and NKRO PS/2.
F21-7d Mechanical Keyboard . 6KRO over USB (no PS/2 option).
Filco Keyboards Listed as NKRO. 6KRO under USB, NKRO with PS/2.
G-Tune Realforce 108B-MP - NKRO over PS/2.
IBM Model F AT: NKRO AT/PS/2 adapter.
iRocks KR-6230. 6KRO with USB.
KBC Poker. 6KRO with USB. NKRO with PS/2 adapter.
Key Tronic KB101 Plus: NKRO PS/2.
Kinesis Advantage: 6KRO under USB.
Kinesis Contoured: 6KRO under PS/2.
Leopold FC200R: 18KRO USB (Windows/OSX/Linux), NKRO with PS/2
Leopold FC500R (FullSize): 18KRO USB (Windows/OSX/Linux), NKRO with PS/2.
Marquardt MiniErgo: NKRO PS/2.
Matias Tactile Pro 3.0: 6KRO USB.
Microsoft Sidewinder X4: 18KRO over USB 
NCR Cherry G80-0528H/10 NKRO PS/2.
NEC APC-H412: NKRO PS/2.
Noppoo Chocolate Min (tenkeyless): Full NKRO under USB and NKRO PS/2.
Noppoo Chocolate Pro (fullsize): Full NKRO under USB and NKRO PS/2.
Northgate Omnikey 101 and CVT Avant Stellar: NKRO PS/2.
PFU Happy Hacking Keyboard: 6KRO under USB. Can not be used with
    PS/2 adapter. 
Qpad MK-80 (Cherry blue): 6KRO with USB, NKRO with PS/2 adapter
    (included).
Qpad MK-85 (Cherry red): 6KRO with USB. Can not be used with PS/2
    adapter.
Raptor Gaming K1: 6KRO under USB. Can not be used with PS/2 adapter.
Rosewill RK-9000 (Gen1, nonremovable cord): 6KRO USB, NKRO with PS/2
    adapter.
Rosewill RK-9000 (Gen2, removable cord): 6KRO USB, NKRO with included
    PS/2 cable.
Steelseries 6G Version 2, 7G: 6KRO USB, NKRO with PS/2 adapter.
Thermaltake Meka G1: 6KRO under USB, NKRO with adapter.
Topre Realforce: 6KRO under USB. Can not be used with PS/2 adapter.
XArmor U9BL: NKRO under native PS/2, 6KRO thru green USB adapter.
XArmor U9BL-S (Cherry Brown): 6KRO USB, NKRO with included PS/2 adapter.
Zenith ZKB-2: PS/2.


The following keyboards support only 2KRO and sometimes even fail to register common game-related keypresses (Source: geekhack.org forum thread (login required), June 5th, 2012):

Cherry Corp G80-3000 (all variations): 2KRO. Fails QWA.
Cherry Corp G80-8200HUAUS-2 (Note: USB Version): 2KRO
Cherry Corp G80-6421 (MX SPOS): 2KRO. Fails QWA.
Cherry Corp G80-MX-11900: 2KRO
Das 2 (Cherry Corp OEM) and Das 1 (Rubber Dome): 2KRO. Fails ASX.
Deck 82 Older Fire and Gold models.
Filco keyboards not specifically listed as NKRO: 2KRO
IBM Model M: 2KRO. Fails ASX, WDE, WAQ, and many others.
iOne Scorpius M10: 2KRO. Fails WASD.
Omnikey Evolution: 2KRO
Omnikey NCS: 2KRO. Fails QAS
Plum 87: 2KRO. Fails WDE, WAQ
Rapoo V7: 2KRO
Razer BlackWidow/BW Ultimate: 2KRO
SteelSeries 6Gv1: 2KRO. Fails QAS, WSD despite being advertised as 8KRO.
Tipro Matrix keypads/boards: 2KRO according to software documentation. 
TG3 BL82: 2KRO. Fails ASW.
Unicomp Customizer 104: 2KRO. Fails WDE, WAQ and many others.
Xarmor U9 - 2KRO - Fails WRV
Xarmor U9W - 2KRO - Fails ASX


"Gaming Optimized" keyboards try to support typical gaming-related key groups, often by giving left-hand keys priority over right-hand keys. Yet even these kinds of keyboards are mostly just 2KRO, and thus sometimes fail to support relevant key groups (Source: geekhack.org forum thread (login required), June 5th, 2012):

ABS M1: 2KRO - fails WAS, WDE, Caps-LShift-S
    (despite being advertised as 6KRO).
Deck Fire 82, Toxic 82, Gold 82 (since corrected in Deck Ice 82): 2KRO.
    Fails QWE.
iRocks KR6820: 2KRO but is optimized for many common gaming key combos.
Logitech G11 : 2KRO. Fails QA-Downarrow.
Logitech Gaming Keyboard G110: 2KRO Fails ZXC, MKL.
Logitech G15V1: 2KRO Fails Rshift-RightArrow-UpArrow,
    Rctrl-DownArrow-LeftArrow.
Logitech G15V2: 2KRO 
Logitech Illuminated Keyboard: 2KRO. Fails Lshift-W-Spacebar.
Microsoft Sidewinder X6 : 2KRO. Fails Ctrl-W-R.
Razer Black Widow (lighted and non-lighted): 2KRO. Fails ZXC.
    Well optimized around WASD/ESDF clusters. Any combo above 2 arrow keys
    fails (note CTRL-AQ does work), ESDF combo.
Razer Lycosa: 2KRO. Fails HJK but passes ASX.
Rosewill RK800G. 2KRO. Can press Q, W, E, A, S, D, space, up,
    left arrow, right arrow, down at the same time.
Saitek Eclipse: 2KRO. Fails QWA, LOP.
SteelSeries 6Gv1: 2KRO. Fails QAS, WSD despite being advertised as 8KRO.
SteelSeries Merc Stealth: 2KRO. Fails ERT, DFG, CVB despite being advertised
    as 7KRO. 
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Coincidentally, the Rosewill RK-9000 is on sale for $63+a free webcam today. I paid $80 for mine, and that was an amazing deal for a cherry MX-blue mechanical keyboard with NKRO. You will likely not find such a high-quality keyboard for so cheap in a looong time. –  BlueRaja - Danny Pflughoeft Jun 5 '12 at 22:30
    
Just tested my late 2012 MacBook Pro's keyboard, it seems it works with any 6 keys I press (it's on internal USB). –  CyberSkull Jul 18 '13 at 5:27

If there is ever enough demand for it, simultaneous keypress support may become a standard stat available, but that is not likely.

I have heard that the SteelSeries Zboard supports many (7 I think) kepresses. Another I have heard is Avant stellar. This discussion might also interest you.

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As StrixVaria pointed out this is a hardware limitation. But you can find a keyboard like you wanted (it will cost more than you usually spend but these keyboards usually tend to last a much longer, easier to type, overall more comfortable and maybe even more healty). The feature you want is usually called as N-key Rollover and modern mechanical keyboards usually have it. . In keyboards that have N-key Rollover each key is scanned independently (These keyboards have an independent mechanical switch for each of its keys and they tend to cost more to produce), so no matter how many keys you press at the time none of them goes undetected.

Check Filco keyboards from Elite Keyboards or Das Keyboard*. I prefer Filco boards but Das looks cooler :). Both of them come in two different switches (well, three for filco but avoid cherry blacks), "Cherry MX Blue" is noisy/clicky (like old IBM Model M boards), "Cherry MX Brown" is quiet. There is a little difference in the feeling but its a matter of taste. Das doesn't use the brown or blue tag, it just calls them normal and silent. Also, if you decide to go with Filco you need to get one which has "NKRO" in its name for N-key Rollover. NKRO is default for all Das keyboards.

If you spend a lot of time in front of your computer (regardless of coding or gaming) I'd advise you to consider this as an investment and get a real keyboard like these :)

*I registered to post this but looks like I can only add one link :/. You have to google for das keyboard.

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I had this problem playing metroid fusion on an emulator but if you map the missle key to alt instad of s so if you are playing on an emulator just remap the key(s)

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Get a gaming keyboard from manufacturers as: Razer, SteelSeries, Roccat, Saytek

These usually support up to 10 keys pressed at once (yeah, all your fingers) and have other neat features into them like lights, audio, USB ports, nice drivers that allow macros to be created and stored.

I'd recommend a SteelSeries Merc Stealth

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In most cases a new keyboard is not necessary, if you have an integrated keyboard in low-end hardware and have recently (re)installed the OS.

Some netbook (and probably cheap laptop) keyboards move some of the usual keyboard logic out of the actual hardware and into software or firmware – critically, the logic that determines which keys are pressed can be lacking in the actual hardware. If the vendor's drivers aren't installed (such as after a user reformats and reinstalls the operating system), no longer being able to chord any keys, even command keys like CTRL and ALT, can be a symptom.

For example, I have a Samsung N130 Netbook, and I used to be able to use the CTRL+ALT+F5 combo to do a forced browser refresh. After a reinstall of Windows XP, I couldn't do this anymore.

The problem was that this low-end netbook's design left half the brains of the keyboard out, and the remains of the brains are in Samsung's drivers.

Though your particular problem – not being able to use any other keys when using two arrow keys – might be a typical hardware limitation of even stand-alone keyboards, low-end integrated keyboards missing the correct drivers can be another source of key chording problems.

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just try and restart you computer. Mine has windows 7 and doesn't work most of the time. But restarting it works.

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The asker has already accepted an answer to this question which he asked 4 years ago. There's no need to put anwsers on old closed questions (and I'm sure he's restarted his computer at least once in 4 years). –  Guy 18 hours ago

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