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Thread: BCM4312 & 4322 intermittence description & work-around for Knoppix 7

  1. #1
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    BCM4312 & 4322 intermittence description & work-around for Knoppix 7

    .
    After three years of faithful service, the wifi in my Dell 1545 Laptop
    began being intermittently troublesome. Left on-line for a few hours
    unattended, I would find the wifi not only dead, but whatever it finds
    in knoppix-data.img would not allow me to get re-connected. I had to
    re-establish persistent store to get on-line again.

    I went to Dell's on-line store, gave them my product ID and found there
    was a re-furbished wifi for $22 plus tax with free shipping. On this
    same site I was able to download an illustrated owner's manual which
    spelled-out how I might easily remove and replace the wifi. The $22
    replacement arrived in a few days and I was able to do the physical part
    of the replacement in mere minutes.

    The wifi provided was not an exact replacement, but a slight 'upgrade'
    from a/b/g to a/b/g/n. The original and the replacement have different
    part numbers, but seem to be operationally interchangeable. The original
    was a BCM4312, Dell part nr DW-1397; the replacement a BCM4322, DW-1510.
    Both Windows 7 and Knoppix 7 easily found and correctly installed drivers.
    The Windows 7 driver installation said, incorrectly, that its install
    was 'unsuccessful'.

    I was pleased with my diagnosis and my bargain and my successful repair.
    For a while, that is. Guess what, the replacement wifi pretty much
    matches the original, including my complaint of infrequent intermittence.

    So, here's a more complete statement of the intermittence. Very
    infrequenly, if I leave my CD-size LiveUSB on-line with no keyboard
    activity I may return and find the wifi connection gone, AND the
    driver unloaded from the Linux kernel. The connection does not re-
    establish itself, even on reboot, without some help.

    There are two simple work-arounds that solve my problem for all practical
    purposes. First, if I notice a dropped connection, I can get back on-line,
    without rebooting, with sudo modprobe b43. Second, I might double-down
    by adding, as root, b43 to my /etc/modules file to make sure b43 gets
    loaded at boot.

    Both the original and the replacement wifis are among those which
    the b43/linuxwireless.org folks say work both with b43 and wl drivers.
    In Knoppix 6.7.1, with the original wifi I never saw this intermittence
    with either driver; however, my experience was mostly with the wl driver,
    I only used the b43 driver for a short time before the advent of Knoppix 7.
    In Knoppix 7, there is currently only a b43 option. I've seen the
    intermittence in both the original and replacement wifis.

  2. #2
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    Continued

    In the event of a router failure, things go from bad to worse.
    Somehow the default Bit Rate for the 4322 gets set to the default auto
    which may in turn deteriorate to 1M instead of 54M in a 'noisy' wifi
    neighborhood.

    I thought I might simulate conditions that would throw wifi off-line
    by interrupting the router, but I find that creates additional problems
    not observed earlier. My temporary remedy for this self-imposed problem
    is to add 'sudo iwconfig wlan0 rate 54M' to /etc/rc.local. It will
    take some detective work to find just where the rate is configured by
    Linux and to change the rate definition more directly.

    I've not seen the original mode of failure, that is, a failure following
    keyboard inactivity, since I added 'b43' to /etc/modules. It may be too
    premature to say that's what has been missing in Knoppix 7, but I notice
    Ubuntu b43 users add this little wrinkle.

  3. #3
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    Recommendation:

    .
    After two weeks of use, I recommend the following minor adjustments to
    Knoppix 7.0.4 to handle infrequent Broadcom BCM-4322 wifi connection
    interruptions using a b43 wifi driver.

    1. Add 'b43' to /etc/modules; and
    2. Add 'sudo iwconfig wlan0 rate 54M' to /etc/rc.local,
    assuming wlan0 is the wifi device in question.

    These adjustments seem to handle my situation adequately.

  4. #4
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    b43 wifi disconnects persist in Knoppix 7.0.5

    .
    Greetings, Fellow Broadcom b43 wifi users.

    I think the new Knoppix 7.0.5 may have a similar problem that 7.0.4 had.

    After a period of wifi connection in a crowded internet environment,
    and no activity,
    I occasionally find my b43 wifi is disconnected, no longer listed on the
    wifi icon list and no longer looking to get re-connected. This is always
    remedied by a reboot. The problem occurs rarely, and perhaps more
    rarely in 7.0.5 than 7.0.4.

    Similar complaints exist over may Linux distros with no real solutions
    offered that I have found, other than the reboot, that is.

    In Knoppix 7.0.4, I thought I might have cured this problem by adding
    b43 to /etc/modules. My hope was that this might aid networkmanager to
    re-install b43 if ever it is removed from the kernel due to inactivity.

    I'd be interested in other b43 users' experiences in 'crowded' internet
    environments, and what if any solutions they may have tried if they have
    encountered this b43-disconnect phenomenon. Probably any Knoppix 7 b43
    has this difficulty to some degree.
    Last edited by utu; 12-27-2012 at 10:49 PM.

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