Looking into it a bit more, I see that 133 is apparently the stock BCLK speed for the i7-950. So the question is why BCLK was 135 under the BIOS Optimized Defaults, before I changed any memory settings. My guess would be that the BIOS tries by default to do some minor OCing, but if you change any timings manually (even just the memory timings), then everything else goes to stock speeds unless you set it otherwise. Does anyone know if that's indeed the correct explanation?