I have an ASUS P8Z68-V PRO, W/ BIOS 1101, 32GB of RAM and I am running Ubuntu precise 12.04.
In the BIOS you can set the amount of memory for the "iGPU", the HD3000 GPU built into my i7-2600K.
I just upgraded to 32GB of ram. Before the upgrade, I had this set to 512, had mtrr_spare_reg_nr=1 and everything worked fine. After the upgrade to 32GB of RAM: mtrr_cleanup: can not find optimal value, please specify mtrr_gran_size/mtrr_chunk_size etc. No matter what I set mtrr_spare_reg_nr to I got this error. However, I found that if I turned the amount of memory for the iGPU down to 256, everything works again.
I have found this to be the case even on the latest git pull, v3.3-rc3.
Other notes, patches, fixes, workarounds: disabling "all memory to be remapped" in bios
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cat /proc/mtrr (256)
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hm, we really shouldn't have a MM/MTRR section here. Oh well.
I recategorised it as x86_64, thanks.
Please try this bug with latest kernel image.