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Author Topic: Keeping up with Logitech n-key rollover keyboards  (Read 7316 times)

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Offline pex

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Keeping up with Logitech n-key rollover keyboards
« on: Wed, 26 March 2008, 14:19:45 »
This is just all part of working for the cause...
Posted on their forum:

http://forums.logitech.com/logitech/board/message?board.id=hardware&thread.id=6217

No responses yet.  I know there is anecdotal references to n-key rollover on SOME runs of the G11/G15, however it is important to note that they advertise, if anything, 'anti-ghosting' rather than 'anti-blocking'...since I'm not big on the science yet, I'd say this is an incomplete reference to n-key rollover (which is also a term companies have used, even if incorrectly.)

In other news, I contacted cherrycorp.com (AGAIN!) for n-key rollover answers.  I don't believe they responsed last time.
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Destroying Sanctity: my Model M project. Status: Dead.

Offline IBI

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Keeping up with Logitech n-key rollover keyboards
« Reply #1 on: Wed, 26 March 2008, 15:55:12 »
I've never heard of a logitech keyboard being advertised with anti-ghosting/anti-blocking/n-key rollover though, do you have a link to that?

Also, don't logitech's keyboards tend to have printed keys?

I got a reply from cherry UK stating that as far as they're aware the G80-3000 didn't have 'Full Alpha N-key rollover'. He did mention cherry had thought about plans for making a gaming keyboard directly, but that any plans for that were shelved for the forseeable future, and advised me to look at the Raptor-gaming K1 and K2 which may have full n-key rollover.
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Offline karlito

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Keeping up with Logitech n-key rollover keyboards
« Reply #2 on: Wed, 26 March 2008, 16:31:02 »
G15 does not support N-Key rollover. It supports 6 keys down + modifiers and that's it.  As far as I can remember it doesnt even come with a PS/2 adapter and it does not work with a PS/2 adapter (at least the ones I have).
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Offline pex

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Keeping up with Logitech n-key rollover keyboards
« Reply #3 on: Wed, 26 March 2008, 16:34:37 »
Cherry has a huge line of keyboards and I have seen some that mention "alpha n-key rollover", which sounds incredibly silly to me but nonetheless I see it mentioned.

"Full" and "Alpha" are not terms that are acceptable together.  "Full" means the whole keyboard, and "Alpha" means the letters.  "Full Alpha" would be redundant and is never the question we should be asking unless that's all we ever expect to need.

Alpha n-key rollover is certainly something I'd never want to support with my buck.  It sounds quite stop-gappish to me.

I am searching for manufacturer references from both Logitech and Cherry to validate my claims...I'll post when I find them.

Quote from: karlito;3771
G15 does not support N-Key rollover. It supports 6 keys down + modifiers and that's it.  As far as I can remember it doesnt even come with a PS/2 adapter and it does not work with a PS/2 adapter (at least the ones I have).

It sounds to me like the 6 key issue is USB-related (although no matter how big the USB buffer is, we should expect that all our presses would show up, right?) as long as it is consistent with all key combinations.  It would surprise me significantly if the G15 couldn't use the PS/2 interface for keyboarding only, and I would find it unfathomable if it couldn't do it with an appropriate driver.
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⌨Ж®Cherry G80-8113 (someday I hope to have one that reads magstripes, rfid cards, and smartcards), ⌨broken \'98 42H1292 Model M, ⌨some other Model M from a decade before that, ⌨30 more keyboards in a box, ⌨4 more lying here or there
Destroying Sanctity: my Model M project. Status: Dead.

Offline IBI

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Keeping up with Logitech n-key rollover keyboards
« Reply #4 on: Wed, 26 March 2008, 18:39:18 »
Quote from: pex;3772

It sounds to me like the 6 key issue is USB-related (although no matter how big the USB buffer is, we should expect that all our presses would show up, right?) as long as it is consistent with all key combinations.


I think it's written into the specifications. Quote from them:

"The keyboard must report a phantom state indexing Usage(ErrorRollOver) in all array fields whenever the number of keys pressed exceeds the Report Count. The limit is six non-modifier keys when using the keyboard descriptor in Appendix B. Additionally, a keyboard may report the phantom condition when an invalid or unrecognizable combination of keys is pressed. "

It's here if anyone feels like reading it in full.

Quote from: karlito;3771
G15 does not support N-Key rollover. It supports 6 keys down + modifiers and that's it.


Hmm, I thought the phrase 'n-key rollover' was a handy way of refering to keyboards that supported more keys than usual but weren't full n-key rollover? If the G15 is proper 6-key rollover then I'm really surprised logitech aren't shouting about it.

Quote from: pex;3772
Cherry has a huge line of keyboards and I have seen some that mention "alpha n-key rollover", which sounds incredibly silly to me but nonetheless I see it mentioned.

"Full" and "Alpha" are not terms that are acceptable together.  "Full" means the whole keyboard, and "Alpha" means the letters.  "Full Alpha" would be redundant and is never the question we should be asking unless that's all we ever expect to need.

Alpha n-key rollover is certainly something I'd never want to support with my buck.  It sounds quite stop-gappish to me.

I am searching for manufacturer references from both Logitech and Cherry to validate my claims...I'll post when I find them.


I've seen mention of Alpha/Full n-key rollover on cherry keyboards too, and I've had people who sell them tell me they've been told that the keyboards have full n-key rollover. However, I've never found reference to it on the cherry site. I wonder if the full/alpha n-key rollover on the G80 is a special order and the normal ones don't have them?

And yes 'Full Alpha N-key rollover' does sound absurd, but that's what the reply I got refered to it as.

I don't think Alpha n-key rollover is stop-gappish. It sounds as if it's for a specific requirement, maybe unicode character entry or multi-lingual writing or something similar. I'd agree that for a general purpose keyboard Full is the way to go.
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Offline karlito

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Keeping up with Logitech n-key rollover keyboards
« Reply #5 on: Wed, 26 March 2008, 21:05:36 »
Quote from: pex;3772
It sounds to me like the 6 key issue is USB-related (although no matter how big the USB buffer is, we should expect that all our presses would show up, right?) as long as it is consistent with all key combinations.  It would surprise me significantly if the G15 couldn't use the PS/2 interface for keyboarding only, and I would find it unfathomable if it couldn't do it with an appropriate driver.


well believe it:
System Requirements
          o Windows® XP, Windows Vista™
          o 256 MB RAM
          o 20 MB available hard disk space
          o USB port
          o CD-ROM drive

This has been talked about before http://geekhack.org/showthread.php?t=163&highlight=saturate&page=4
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Offline pex

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Keeping up with Logitech n-key rollover keyboards
« Reply #6 on: Wed, 26 March 2008, 21:56:13 »
Quote from: karlito;3774
well believe it:
System Requirements
          o Windows® XP, Windows Vista™
          o 256 MB RAM
          o 20 MB available hard disk space
          o USB port
          o CD-ROM drive

This has been talked about before http://geekhack.org/showthread.php?t=163&highlight=saturate&page=4

Inability to use a USB-to-PS2 converter, which are readily available and have in recent past years been readily distributed from keyboards, is not discussed as far as I can see.  There is talk about the USB spec and buffering with regards to keyboard input.

Many people will say that the G15 isn't PS/2 compatible because, for example anyway, the LCD screen won't work.  Logitech will, of course, agree.  It's going to be tough to find out if just keys work on the the PS/2 interface without someone clearly addressing that specifically.  I won't accept supposed anecdotes on n-key rollover functionality based solely on a non-working LCD display without clear evidence they are speaking inclusively of the keys.

As for questions about n-key rollover, "n" is any number.  Put a number in and the board can handle it.  The interface is not figured into this; the limitation will be decided inside the hardware (the controller or assembly); it is only convenient to test through an interface, which will have its own limitations to be described elsewhere.  Here, we know the PS/2 can handle a mass of data serially, pretty quickly, and I see no reason why a keyboard could not just queue presses in a controller and send 6 at a time.

Essentially, none of our interfaces should trouble our testing for n-key rollover.  Even if USB has a limitation on 6 keys, if you try EVERY combination of 6 keys on the keyboard and they all register, that is a good case for n-key rollover if not an empirically tested one.
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⌨Ж®Cherry G80-8113 (someday I hope to have one that reads magstripes, rfid cards, and smartcards), ⌨broken \'98 42H1292 Model M, ⌨some other Model M from a decade before that, ⌨30 more keyboards in a box, ⌨4 more lying here or there
Destroying Sanctity: my Model M project. Status: Dead.

Offline Whiskey in the Jar-o

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Keeping up with Logitech n-key rollover keyboards
« Reply #7 on: Thu, 27 March 2008, 06:08:50 »
USB keyboards not being usable via a PS/2 adapter is nothing new.  For example, the MS Natural 4000 is USB-only.
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Offline pex

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Keeping up with Logitech n-key rollover keyboards
« Reply #8 on: Thu, 27 March 2008, 14:34:15 »
Quote from: Whiskey in the Jar-o;3779
USB keyboards not being usable via a PS/2 adapter is nothing new.  For example, the MS Natural 4000 is USB-only.


I don't suggest that this is impossible.  I just don't believe it is a subject likely to be addressed by most summaries of compatibility and would best be answered by first-hand-testing or the manufacturer by direction question.

http://forums.logitech.com/logitech/board/message?board.id=hardware&thread.id=128

It would still be nice to hear about a first-hand test.
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⌨Ж®Cherry G80-8113 (someday I hope to have one that reads magstripes, rfid cards, and smartcards), ⌨broken \'98 42H1292 Model M, ⌨some other Model M from a decade before that, ⌨30 more keyboards in a box, ⌨4 more lying here or there
Destroying Sanctity: my Model M project. Status: Dead.

Offline IBI

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Keeping up with Logitech n-key rollover keyboards
« Reply #9 on: Thu, 27 March 2008, 15:18:45 »
Quote from: pex;3784
I don't suggest that this is impossible.  I just don't believe it is a subject likely to be addressed by most summaries of compatibility and would best be answered by first-hand-testing or the manufacturer by direction question.


Why is PS/2 compatibility important on something like the G15?
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Offline pex

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Keeping up with Logitech n-key rollover keyboards
« Reply #10 on: Thu, 27 March 2008, 15:33:38 »
Quote from: IBI;3786
Why is PS/2 compatibility important on something like the G15?


I haven't seen conclusive results that any keyboard does appropriate queuing of keypresses beyond 6 keys on the USB interface.  We know that the PS/2 can provide a more accurate view on rollover.
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⌨Ж®Cherry G80-8113 (someday I hope to have one that reads magstripes, rfid cards, and smartcards), ⌨broken \'98 42H1292 Model M, ⌨some other Model M from a decade before that, ⌨30 more keyboards in a box, ⌨4 more lying here or there
Destroying Sanctity: my Model M project. Status: Dead.

Offline IBI

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Keeping up with Logitech n-key rollover keyboards
« Reply #11 on: Thu, 27 March 2008, 18:49:23 »
Quote from: pex;3788
I haven't seen conclusive results that any keyboard does appropriate queuing of keypresses beyond 6 keys on the USB interface.  We know that the PS/2 can provide a more accurate view on rollover.


I thought someone had proved here that the HHKB pro 2 could do full n-key rollover, but as I can't find the post maybe I'm imagining things. :eek:
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Offline zillidot

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Keeping up with Logitech n-key rollover keyboards
« Reply #12 on: Fri, 28 March 2008, 18:44:53 »
Quote from: IBI;3794
I thought someone had proved here that the HHKB pro 2 could do full n-key rollover, but as I can't find the post maybe I'm imagining things. :eek:

I think you are. :) From what I remember it's subject to the same limitations of USB as any other keyboard.

Oh well. It's good enough for me to have every 6 key combination work. :)
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My keyboards:
Realforce 87U (all 55g)
HHKB Pro 2 (black on black)
Filco Majestouch (n-key rollover, brown cherries)
Unicomp Customizer 101 (black with black keys)

Offline pex

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Keeping up with Logitech n-key rollover keyboards
« Reply #13 on: Fri, 04 April 2008, 04:40:13 »
The word from Logitech Support:

1. DiNovo Edge Keyboard
2. DiNovo Media Desktop Laser


Not impressive.
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Destroying Sanctity: my Model M project. Status: Dead.

Offline pex

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Keeping up with Logitech n-key rollover keyboards
« Reply #14 on: Sat, 10 May 2008, 14:55:20 »
Made a call to the consumer sales line the other day, the operator made a suggestion to me that their scripts didn't have that information yet went on to suggest that G11/G15 probably does.  I told him I'd heard anecdotes of this but that data is obviously not on the tech specs page.

I asked if he would put in a suggestion to marketing that this be added if it were true.  He harvested my name and number, but in a bum move I gave him bad info, so there could be no follow up (if such a thing was planned).
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⌨Ж®Cherry G80-8113 (someday I hope to have one that reads magstripes, rfid cards, and smartcards), ⌨broken \'98 42H1292 Model M, ⌨some other Model M from a decade before that, ⌨30 more keyboards in a box, ⌨4 more lying here or there
Destroying Sanctity: my Model M project. Status: Dead.
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