I've been toying around with roms for a few weeks and just recently noticed this. When using setCPU to overclock and having the phone charging via an AC outlet, the phone never reaches the min speed and never goes below 500mhz. This does not happen when charging via USB (tested it on two computers and my car USB with three different cables, and yes I verified it was charging on all three). SetCPU is on auto-refresh.
I always run all profiles with a min setting of 250mhz (main screen too). Now the green numbers say the correct values, but the white number will never drop to the min setting, or even below 500mhz. I can change the main screen to 250/250 and it still stays at 500mhz while charging via AC. I can change charging profile to 250/250 and it still stays at 500mhz also. Unplug the charger and it will drop to 250mhz with no problem. Plug it in and it goes right back up to 500mhz.
Someone mentioned that SetCPU does not refresh automatically when plugging in while it is running on the screen and maybe that was it. I verified this was untrue, because on a setting of 250/600 I drag the notification bar to cause it to ramp up to 600mhz and then back down to 500mhz and I can see it. Even so, I went ahead and closed out SetCPU, plugged the charger in and opened up SetCPU after. Still at 500mhz.
I also ran SeeCPU while in SetCPU to see if maybe something was running the cpu up while charging. It runs around 5% - 10% cpu load while doing nothing, yet still at 500mhz.
So, I did more testing. I tested both Cyanogen 184.108.40.206 and Smoked Glass 6.0.1 roms and multiple kernels. I wiped BOOT, SYSTEM, CACHE and DATA before each install. They ALL did it. The only difference was that the minimum speed changed depending on the kernel. The faster the kernel, the faster the minimum speed. One would not go below 700mhz when plugged in to AC.
I have to assume this is a SetCPU thing. Is this supposed to happen? I would think the phone would charge faster if it didn't. Is it intended or a bug? Can anyone else out there check their phone when plugged in to AC (NOT USB) and check what their white number says?