As promised, I'm back with some more testing. For cgminer, I used the data reported by the interface. For phoenix, I redirected out put to a log file and calculated the time since the "connected to server" message and last "accepted" log for the sampling period and used that to determine the accepted shares/minute indicator.
And all this complicated math and monitoring gave me these conclusions:
* [expected] at the same GPU frequency, cgminer and phatk-0711 hashrates are about the same.
* [expected] as frequency increases, hardware errors increase at a greater rate in cgminer, than for phatk-0711.
* [UNexpected] increases in hardware errors don't affect hashrate increase by frequency increase. I would have expected that bumping the frequency in cgminer would bring me *less* hashrate increase than phath-0711. Rationale was that more hardware errors would "eat" from hashrate. But there's no visible effect, so bumping the frequency seems to be prefferable, and hardware errors can be ignored (well, unless the board melts
* [expected] also, more hardware errors won't lead to more rejects. Rejects are more related to communication problems with the pool than local conditions. That's why I ignored them in all my calculations.
* [UNexpected] even for 10.000 accepted shares samples, hashrate/hardware errors/frequency has less than expected impact on accepted shares/minute. Variance is high and depends a lot on network conditions. It's impossible to assess that running the card at +5% frequency/hashrate will increase your accepted shares by 5%. Might even decrease it
Soooo.... yeah. Not exactly what I expected, but not unhappy either. It just means that one can run almost any kernel at any frequency and will get about the same results (more influenced by network conditions and pool luck rather than hardware settings of kernel optimisations). Some will prefer to keep it cool (the board, I mean) using a lower frequency and consuming less power, others will tweak the last ALU op and last Mhz our of the board. Just because they can. You know where I stand
On an even happier note, the latest phatk mod by @Diapolo, 08-04, brings back the hardware errors to 07-11 levels, so my original problem will go away when this kernel will be ported to cgminer.