[coreboot] Changing DRAM Frequency

Rudolf Marek r.marek at assembler.cz
Wed Aug 17 20:54:14 CEST 2011

> I am aware that coreboot initializes DRAM and sets its frequency (cache-as-ram)
> during boot. I would like to know if it is possible to change the DRAM frequency
> by following the same initialization sequence without rebooting the system
> (along with preserving the application's memory context).

Yes I had similar thoughts and I think it could work like this:

1) Execute code from ROM
2) There, issue the self refresh cycling to memory controller
3) turn off clocks for memory
4) do whatever else
5) restore clocks/just exit from self refresh (same code as S3 resume)

In theory it could be possible to shift frequency / settings this way, however 
DQS strobing fine tunes might make it impossible.


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