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n-key rollover problems with a Logitech keyboard

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February 18, 2004 7:06:15 PM

I searched the forums here and noticed several other people having similair problems to this, but they all seemed to have offered very poor explanations and put forth very little effort in resolving the problem themselves, so I figured I would more proplerly explain what the problem is:

I was recently in need of a new keyboard for the gaming rig I just finished assembling, and having been pleased with Logitech's MX500 mouse, I figured a Logitech keyboard would fit the bill nicely. So I went ahead and threw down the cash for <A HREF="http://www.newegg.com/app/ViewProductDesc.asp?descripti..." target="_new">this keyboard</A>. I received my new keyboard within 2 days as I do with any order from NewEgg, and hurriedly plugged it in to test it out in a game of Counter-Strike. Any of you familiar with the keys required to play Counter-Strike know that in order to Walk or Crouch you need to hold down the Shift and Ctrl keys, respectively, and often times you will want to move in one or more directions while performing one of these activities. I started to notice that whenever I tried to Crouch/Walk while moving forward (w-key) and strafing to the right (d-key) simultaneously, the last key I pressed would not respond.

I further investigated this phenomenon, insuring that Microsoft and their god-damned Sticky Keys or any of my BIOS settings weren't causing the problem, and resigned that the issue was definately hardware, more specifically the keyboard, related.

I contacted Logitech's Technical Support only to receive the generic response:

<i>'Have you installed the newest drivers?'</i>

I responded informing them that I had indeed installed many versions of their drivers, and received no satisfactory results. The next response, which I noticed was from a different representative, stated that:

<i>'Unfortunately, this keyboard is not compatible with the Windows XP machine. There is no driver for this keyboard in Windows XP environment.'</i>

What the [-peep-] do you mean my keyboard isn't compatible with Windows XP? It states very clearly on nearly every side of the manufacturer's box that I received the keyboard in that it was not only compatible, but <b>designed</b> for Windows XP. After contacting them <i>yet again</i>, I finally got ahold of somebody who knew what they were talking about, and received the following response:

<i>We are sorry to know that you are not able to use some combination of keys with the Logitech Keyboard. All our keyboards use a membrane technology without diodes. The detection scheme that is used is often called multi-key rollover.

Our keyboards can detect any 2-key combination but not all the 3-key combinations. We place the keys in the matrix in order to guarantee that the 3-key combinations required by Microsoft are supported. Basically we support any combination of 2 modifier keys (LWIN, RWIN, LCTRL, RCTRL, LSHIFT, RSHIFT, LALT, RALT) plus one other key pressed at the same time (there are a few exceptions to this rule).

It's true that a gamer who needs to press some keys simultaneously might encounter a ghost key situation. In this case the keys are not reported to the PC until the ghost key situation is cleared. A full n-key rollover keyboard would avoid this problem. However, these keyboards are more and more difficult to find on the market because of their higher cost (they need one mechanical switch and one diode per key).

We once again apologize for the inconvenience.</i>

I didn't even know this phenomenon [-peep-] <i>existed</i>. I find it hard to beleive that Logitech would have such an incredible peice of game oriented mousing machinery as the MX500, yet for some reason their keyboards can't support one of the most common key combinations used in the very game that their mouse seems to be the <b>most popular</b>.

Have any of you experienced this problem with a Logitech Keyboard? Does anybody have any idea if there is some sort of workaround for it? Or, does anybody have a recommendation for a keyboard that has proven itself for an application like Counter-Strike, and is available in black?
February 18, 2004 7:25:56 PM

This is basically the same as what I replied <A HREF="http://forumz.tomshardware.com/hardware/modules.php?nam..." target="_new">here</A> but without the fancy words.
The array architecture all keybords uses allows it (as explained above) to detect all simultaneous 2-keypress situations (NOT including qualifers CTRL, ALT and SHIFT which are not part of the array) and some (but not all) 3-keypress situations. All keyboard have this problems, although which 3-keypress situations that can be resolved may differ from one keyboard to another since the keys may be organised differently in the array.
This is <i>not</i> a driver issue. The driver has nothing to do with how the keyboard array is scanned. The driver only interprets the commands from the keyboard. It the keyboard itself thats incapable of resolving multiple simultaneous keypresses.

<i><b>Engineering is the fine art of making what you want from things you can get</b></i>
February 18, 2004 9:55:02 PM

thats a cheap keyboard man. i have a ms natural keyboard and i have never had any problems like that. i have with cheaper keyboards though.

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February 19, 2004 4:45:54 AM

here are some keyboards and some keyboard manufacuters that advertize n-key (alpha n-key) rollover. most of them are designed for industrial/business purposes.

fujitsu seimens (the fujitsu kbc p2)
maxim adjustible
anewtech
cherry G81-8000 and several other cherry keyboards

look <A HREF="http://www.keyboardgalaxy.com" target="_new">here</A> for more options.
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