By Zah Lee. date: Last updated: ,
What is N-key rollover?
N-key rollover (NKRO) is the number of simultaneous key presses that can be recorded by a keyboard.
6-key rollover means that up to 6 keys can be pressed simultaneously. Full N-key rollover means that the keyboard can correctly detect any number of key presses simultaneously.
What is the main ghost?
key ghost This happens when multiple keys are pressed but wrong keys are registered.
What is anti-ghosting tech?
Some gaming keyboards, such as the Microsoft SideWinder (year 2010), have so-called “anti-ghosting” technology. Basically, it’s designed to let you press multiple keys at once, but it’s not an actual hardware NKRO.
Unlike partial anti-ghosting solutions that have multiple combinations of 3 keys that don’t work, Microsoft’s Sidewinder X4 has multitouch technology that allows it to detect and report any combination of QWERTY keys up to 17 keys. Additionally, it can report 7 modifier keys, 1 hot key, and 1 macro key, bringing the maximum number of reported keys to 26. See the Sidewinder X4 Anti-Ghosting FAQ for more information.
,Microsoft Sidewinder X4 Anti-Ghosting FAQ ,
http://www.Microsoft.com/appliedsciences/content/projects/SideWinderX4.aspx,
Test how many keys your keyboard can register
press and hold both left shift key and right shift key, then press xSee if the letter appears on your screen,
Yes? Now, try other keys, while keeping both shift Keys depressed. Read the entire alphabet. It’s best to ask your friend to help you hold down both Shift keys.
On my Microsoft Comfort Curve Keyboard 2000 and Natural Ergonomic Keyboard 4000, when both shift the key is placed down x And , And 3 do not work!
On my Apple iMac keyboard M2452 (year 1999), all top row {Why w E R Tea Y You I hey P [} does not work, except ] And ,,
Same result on my Apple keyboard A1048 (year 2003).
N-Key Rollover, Key Ghosting, Keyboard Switch Circuit Design
The matter is quite complex. This has to do with the cost-saving design of the circuit and the keyboard interface protocol (such as USB).
Ideally, each key is an electronic switch. When a key is pressed, a signal is sent to that key. This is logically simple, but it is an expensive way to design a circuit.
Instead, the keys’ electronics are laid out on a rectangular grid. When a key is pressed, it combines the row and column the key is on. This row+column determines which key is pressed. This way, you don’t need a switch per key. Suppose you have 30 keys on a 3×10 matrix. With one switch per key (full N-key rollover), you need 30 switches. But with the grid approach, you only need 3+10=13.
Grid approach to keyboard circuits. ,anti-ghost interpretation , http://www.Microsoft.com/appliedsciences/AntiGhostingExplained.mspx,
The problem with the grid approach is that when multiple keys are being pressed on the same column or row, there is a problem in knowing which new key is actually being pressed. So it may not register the key you pressed, or send an adjacent key that you did not press. (That’s why it is called ghost)
This is a simple design flaw of the circuit, and can be easily fixed, however, fixing this problem so that all keys are recognized correctly when pressed simultaneously means more electronic components, more cost. But most people don’t need to press more than 3 keys at the same time anyway, so keyboard manufacturers don’t bother with perfect solutions. They simply create some additional grids for different groups of keys and or rearrange the correspondences between keys and positions on the grid, so that common key combinations do not occur in the same column or row.
Modifier keys, for example, {alt, Ctrl, shift}, often needs to be used with other keys. Therefore, keyboard manufacturers have ensured that there is no issue with multiple keys with these. But unusual combinations, like pressing both left and right shift Plus other keys, practically never used. So they become victims.
USB connector and NKRO
The USB interface can theoretically detect any number of keys pressed simultaneously. But in practice, due to lazy implementation, most non-gaming USB keyboards default to “boot protocol” in USB, so only a maximum of 6 keys pressed simultaneously can be detected.
PS/2 connector and NKRO
The IBM PS/2 interface (popular from 1990 to ~2010) can always detect any number of keys pressed simultaneously.
Which keyboards have full N-key rollover?
Most high-grade keyboards have full N-key rollover. But the only easy way to know is to actually test it.
Non-gaming keyboards from Microsoft, Logitech, Apple do not have n-key rollover.
Who needs to press 6 keys at once?
Stenotype, Braille, and many computer games all require full NKRO.
Braille2000, see:
To use any computer braille-entry program, including the Braille2000, you will need a keyboard that responds to six-key input. Be aware that many popular brands of computer systems come with keyboards that are not compatible. Be especially careful when shopping for a laptop computer, not being able to use its built-in keyboard will be a real bummer.
[from http://www.braille2000.com/brl2000/KeyboardReq.htm ]
Why is it necessary to press more than 6 keys simultaneously in computer games?
The need to press more than 5 buttons simultaneously is common in gaming. Typically, the arrow keys or WASD keys are used to control your character’s movement. shift The left/right arrow makes your avatar move left/right instead of turning left/right. Sometimes 2 arrows such as Up/Right arrow will force your avatar to move diagonally. Add keys for jumping or crouching, usually requiring a combination with the avatar movement keys. Add a key for run mode. Then, there’s also things like firing a gun, firing a shield, all at once you have 5 or 6 keys pressed simultaneously.
Basic modern keyboards have already moved their electronic grids so that multi-key combos with modifiers are not a problem. But when the game or gaming becomes advanced, like doing some stiff shooting during prime jumps etc. like in Second Life, you need a keyboard that performs well. For this reason, as cited by Microsoft and elsewhere, gaming keyboards often take extra effort to get it right.
As another example, I remember about 10 years ago, I could play Street Fighter in 2 player versus mode on PC. For single player, you need 4 keys for movement and another 4 or 6 for different levels of kicks and punches. For two people playing on the same keyboard you really need a keyboard that can correctly detect 20 keys simultaneously. Remember to input those super combos to execute special attacks. laugh out loud
N-key rollover and Emacs
Discovered a dead key. In Emacs, I have ▤ Menu The key is set as hyper, and I have
Extreme,shift,x As a shortcut to a command. However, Microsoft Natural Ergonomic 4000 does not register that combination as correct. shift Used, but abandoned shift Works. 〔See Emacs key: super hyper〕