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#289852 - 16/11/2006 13:22 Linux help.
insightful
new poster

Registered: 21/11/2001
Posts: 40
Loc: Maine, USA
I am having an issue with keystroke repetition in Linux. I have tried different keyboards with the same result, so my guess is a driver issue. My system administrator hasn't had any luck finding a solution thus far, so I thought I'd try posting here. Anyhow, the problem is that, periodically, single keystrokes become multiple keystrokes. For example....

ttttyyyypppppiiinnngggg rrrraaaaaandom words to show how ttttthhhheeeee ppprroooobbbblllleeemmmm sssshhhhoooowwwsss iiiitttttself. iiitttt dddoooeeeessssnnnn'''t haaaaapppppppeeeennnn aaaaalllllllll the time, but often enough ttttoooo bbbeeeee aaaa rrrrreeeeeaaaaaallll pppaaaiiiinnnn iinnnnnn tttthhhheeeee aaaaassssssss....

It seems to be random in occurrence and duration. I don't have root access, so I will have to forward any suggestions to my sys-ad.

If it makes any difference, the machine is an HP xw9300 with dual AMD Opterons, running Red Hat (2.4.21-27.ELsmp from uname).

Typing this message sucked.

-Jeff

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#289853 - 16/11/2006 14:36 Re: Linux help. [Re: insightful]
Roger
carpal tunnel

Registered: 18/01/2000
Posts: 5683
Loc: London, UK
Do you have any other problems, like clock drift? I had a similar problem with my AMD X2 chip, where I'd get keyboard repeat.

I was also, at the same time, seeing clock drift. I fixed the clock drift with a kernel command-line option (which I can't remember -- I'll dig it out if necessary), which also fixed the keyboard repeat problem.
_________________________
-- roger

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#289854 - 16/11/2006 14:37 Re: Linux help. [Re: insightful]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
USB or PS/2 keyboard? Does dmesg have anything to say about the keyboard? Just in X-Windows or in the console, too?
_________________________
Bitt Faulk

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#289855 - 16/11/2006 15:01 Re: Linux help. [Re: Roger]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 14496
Loc: Canada
Quote:

I was also, at the same time, seeing clock drift. I fixed the clock drift with a kernel command-line option (which I can't remember -- I'll dig it out if necessary), which also fixed the keyboard repeat problem.


Ahh.. the infamous "unsynced TSC" problem, perhaps. Where one CPU grabs a timestamp from its TSC, representing the key "press".. and the other CPU eventually compares against its current TSC to see if it's time to generate "repeats".

If the two TSCs are not perfectly synchronized, then the keyboard repeat can go all to he**

This is apparently only a problem on AMD processors at present..

Disclaimer: I don't actually know if the keyboard driver uses the TSC for its timestamps; this example was just to illustrate the potential problems

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#289856 - 16/11/2006 15:04 Re: Linux help. [Re: mlord]
Roger
carpal tunnel

Registered: 18/01/2000
Posts: 5683
Loc: London, UK
Quote:
Ahh.. the infamous "unsynced TSC" problem, perhaps.


Yep. That's what I was seeing. I added the following to my kernel command-line options and both the clock drift and the wonky keyboard repeat went away:

Code:
clock=pmtmr

_________________________
-- roger

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#289857 - 16/11/2006 15:40 Re: Linux help. [Re: Roger]
insightful
new poster

Registered: 21/11/2001
Posts: 40
Loc: Maine, USA
I have tried both USB and PS2 keyboards. Also, rebooting sometimes fixes the problem and it will be gone until the next reboot. I have not noticed clock drift, but that doesn't mean it's not happening. I'll try to be more aware of it.

Thank you all for your help. I'll pass the info along to my sys-ad.

-Jeff

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