What I’ve found is that the new Power Scheme found in Cubase 6 improves the PCI latency a lot, and it also improves the efficiency on low latencies with multiple CPUs by a large amount. I’m using an RME Fireface 800 with a buffer of 64 samples only for real time playing.
Turning on the old option in Cubase 5 does not affect my system at all, if I’m running it with the default Windows full power scheme. Analyzing the PCI latency with PCI Latency checker shows no change (lots of spikes, maximum of 567us here, usually 250us). The ASIO performance monitor shows no improvement either. I suppose this option is only meant to disable any power saving feature you may have set for default in your system, without doing anything more.
However in C6, turning the option on, the PCI latency stabilizes incredibly,with a maximum of 230us and usually around 120. The ASIO performance monitor also reflects this. Of course it also sets the entire system to consume more power (I measured 10 watts more than using the default full power scheme). The option does what it says, improves stability with low latency settings and multiple CPUs, and makes the PC to consume more power. There is nothing broken, all the contrary, THIS IS GREAT! you can have more power and audio stability than any other way. I would like to know what’s the improvement so I can use it to play games too 
But, I wouldn’t recommend turning this option ON if your system is not well refrigerated. Now I need a new CPU cooler!
Cheers,
Alberto
