Today I have been focusing on the DEH-2000A-A, which is a 21xx prototype. So I haven't looked at overclocking yet. Was going to, but we'll see what I get time for.
Specifics. The LV1 rsx string contains the Hex representation of the VID. like 0x22. Convert that to binary and it can be looked up in the VID table of the datasheet for the buck controller. What
@M4j0r found were the addresses in syscon eeprom that you can write that hex value to, and that will be used to select the RSX voltage.
Here's the problem and reason I've not yet released specifics. The VID tables I made to map the hex VID to the binary vid that encodes a specific voltage are not matching up perfectly with every RSX VID that I'm seeing in the 150 or so consoles I've recored the LV1 rsx strings. For example, my surtees has a VID of 0x2B which would map to 1.375v and that's WAY too high. I don't trust what my table is saying that is supposed to be. But it works for most consoles in the 20 to 28 range. I'm trying to figure out why.
I dont want to release the tutorial until I'm reasonably sure the VID tables I made arent going to cause you to think you're changing from 0.900v to 0.910v, only for it to jump to 1.600v and fry your console!