I'm trying to figure out exactly what the "APM Master Mode" feature does when enabled in my BIOS (Gigabyte 970a-D3 MB).
I've got a FX-4100 processor and most of the documentation on this setting is really lacking or nonexistent. Based on what I've read, it sounds like APM master mode does pretty much the same thing that AMD K8 Cool&Quiet does... So what's the difference?
I'm not an expert, but I've been experiencing similar problems myself and I believe I understand what AMD APM Master Mode now is now, and how it differs from AMD Cool and Quiet.
According to my understanding of the article "AMD FX Processors Unleashed | a Guide to Performance Tuning with AMD OverDrive and the new AMD FX Processors", linked here: http://sites.amd.com/us/Documents/AMD_FX_Performance_Tu..., AMD APM Master Mode (APM) seems to work with Turbo Core to change clock speeds and voltages to stay within thermal and power limits. More specifically, APM seems to limit power consumption and thermal output to set limits, but this doesn't necessarily mean it always underclocks. It seems that in combination with Turbo Core, as long as your voltage AND thermal output for your processor are below a set limit (don't know where it's set), APM will allow Turbo Core to overclock cores to the limit set by the Turbo Core setting, as long as it doesn't exceed the voltage and thermal limit for APM.
This is different from AMD Cool and Quiet, which I believe primarily lowers voltage and clock speed if CPU cores are idle.
Again, I am not an expert, but I'm presenting my understanding of the technologies as it seems likely to me I get the general gist of how they work, but I may be wrong. And check that link up there, I think it will have a good bit of the info you need (do a search for APM). Hopefully this at least helps you in your search to understand the technology.