I recently discovered that an ancient laptop built by Mtech and containing an
AMD K6 450/2 CPU was generating errors when using the Cardbus versions of
Broadcom cards using either b43 of b43legacy. Expecting some change in those
drivers or ssb, I found a kernel old enough to work without the error, and did a
bisection. I was very surprised when "x86: merge tsc calibration", which is
commit bfc0f5947afa5e3a13e55867f4478c8a92c11dca (dated July 1, 2008), turned out
to be the source of the regression. It was verified by generating a reversion
patch. One main difference is that the bad code gets a processor speed of
214.398 MHz, whereas reverting the commit yields 428.845 MHz, which is more in
keeping with the stated frequency of 450 MHz. As the machine is more than 10
years old, the clock may have drifted considerably.