I have tried the same homebrew serial on two different machines.
One one machine (1 core UP) 'xmode2 -m -t 1' produces a very stable waveform, and irw works reliably.
On the other machine (Asus M3N78-EM, 4 core Phenom, 64-bit) the waveform is not stable and irw works very unreliably.
(Linux myth-htpc 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:58:03 UTC 2009 x86_64 GNU/Linux)
I was wondering if there were any settings/attributes that could be passed to improve waveform stability. I have a feeling it is related to how interrupts are processed.
I have tried off-lining 3 out of 4 CPUs and also binding IRQ3 (lirc_serial) to a single CPU, no effect.