Crippled chords without a Full N-Key Rollover

Identifying the problem

What do writers, gamers and trackers have in common? You type so fast that you hold the keys before they appear on screen. The word "the" is so common, you simply press all three keys are pressed at once. But what happens with lenghtier words? BEEP! Or imagine, your rocket launcher refuses to fire because you are doing a diagonal doublejump in a First Person Shooter. It could mean the end of your virtual life. And you probably have noticed chord playing does not always go smoothly with the pc keyboard: when you play some chords, some notes are missing. This specific example was brought up in the forum topic Playing Chords. In summary: certain combinations of keys are blocked. Specific groups of people experience that same problem. But is the software to blame, or the hardware?

Hold e-r-x-c

If you have no idea what I am talking about, imagine being able to press at most one key at a time. That is what it means for a keyboard to have no "rollover". Try entering different combinations of alphanumeric keys in the textbox, like r-y-u and e-r-x-c. All keys have to be pressed at the exact same moment.

Keys accepted:

A good keyboard with a so-called full n-key rollover should allow you to enter all keys simultaneously.

What is causing keys to be blocked?

In the days of old (the digital world is moving fast), each key press was interpreted independently. Regardless of the number of keys pressed, all keys would have been accepted in the correct order. This property is called full n-key rollover. Key rollovers come in various types. Full n-key rollover is the least restrictive type: each key has dedicated electronics. Alpha n-key rollover refers to alphanumeric, which includes all letters and numbers. The "n-key" part means that any number of keys can be pressed simultaneously. Full n-key rollover keyboards are nowadays hard to find. Over the course of years, keyboard manufacturers have sought to simplify the keyboard design. They save $0.07 per key by replacing the individual diodes of each key with a matrix of key switches. The simplified design allows only the most frequently used key combos. Modern keyboard, including those expensive multimedia keyboards, are typically 3-key rollovers. Some manufacturers advertise the shortcoming as a feature, eg. "Phantom Key Surpression".

Where can I get a full n-key rollover keyboard?

Relatively few people need more than a 3-key rollover keyboard, so we can skip all mainstream keyboards. We will have to move on to niche markets. Gaming keyboards cost more than $100. Usually too big and bloated for tracking. On the other hand, manufacturers will think twice selling crap to (semi-)pro gamers. They risk upsetting the complete gaming community.

• Razer Tarantula10-key "anti-ghosting"
• Logitech G15/G11 Full n-key (Update: 6-key + modifier)(Update 2: no rollover at all?!)

Office keyboards. Really, I expected more from this category. Aren't professional writers annoyed with 3-key rollovers? And what about braillists, who need at least a 6-key rollover?

• Fujitsu-Siemens KBPC PX Stopped being full-n key in 2004.
• IBM Model M (Update: rollover may vary per series) This rarity is the cream of the crops, because/but it clicks very loudly.
• Cherry G81-8308 Alpha n-key. Expensive, about $140!
• Das Keyboard A modern reincarnation of the IBM Model M, $129. The Ultimate version has blank keys :D
• Majestouch Tactile Touch NKRO USB keyboard with 6-key rolloever; full n-key rollover when connected through PS/2
• Happy Hacking Keyboard Minimalistic 60 key layout. Sexy. Built-in USB hub. And a maximalistic price.

All keyboards listed are supposed to have full n-key rollover. Do not take my word for it and do your own research. Having experienced myself, "should" does not equal "is". When purchasing a keyboard, make sure you can return it. If you can suggest me any interesting keyboards, I will list them here.

Pitfalls

• A PS/2 to USB converter may not be able to handle the required data throughput.
• The type number does not guarantee that every product bearing it is the same. Specifications change occasionally and may very per region.
• Data sheets do not necessarily match the actual specifications.
• Customer support people do not know, nor care. They will sell you a 3-key for a full n-key. Yes, I am still bitter.

In the end, we are still looking for a cheap full n-key rollover keyboard with a USB connector. Perhaps a business opportunity?

Update

The USB protocol limits the n-key rollover to a maximum of 6. There are now some USB keyboards that are capable of full n-key rollover, but only when the PS/2 adapter is used. Check out EliteKeyboards, they sell the Majestouch Tactile Touch NKRO, and Happy Hacking Keyboards.