BC-250 tool to set CMOS BIOS memory configuration from linux. Works also with original P3.00 and P5.00 BIOS, no modded BIOS needed.
Either you build it from source or you can get the bc250_memcfg.zip zip from releases with binary executable already compiled.
The most useful parameter to set is probably VRAM size (UMA_SIZE)
you run it as root with one parameter and value like this
sudo ./bc250memcfg UMA_SIZE 512
setting UMA_SIZE to 512
and then reboot the machine.
For UMA_SIZE you can use any sensible value >= 256, the number gets automatically aligned to 16MB steps.
Running without parameters prints all values for all tunable parameters.
You can also tune memory timings (like tREF) but it may affect stability and no significant gains were confirmed. For more info see https://github.com/NexGen-3D-Printing/SteamMachine/blob/main/Memory-Timings-Explained.txt
This tool writes to battery backed CMOS RAM. To revert to default values clear CMOS by jumper on the board and/or by removing battery.
This tool does not require modified BIOS, it was confirmed that it works both with P3.00 and P5.00 original BIOS so no custom BIOS is needed if you just want to modify VRAM size.
Initial source version of this utility was published on Discord in Mem Timing Utility topic by ethkey. It printed all parameters and hardcoded 'demo' writing of tREF was causing segfaults. I just fixed the crash and added code to set value for each tunable parameter via command line.