[coreboot] 8 GB DIMMs on Nehalem (Arrandale)

[Charlotte Plusplus]

Addressing over 8G is not supported by the chipset used on nehalem thinkpad
laptops (X201)

Stupid limitation, but it is not the CPU fault.



On Sat, Jan 21, 2017 at 5:55 AM, Stefan Tauner <
stefan.tauner at alumni.tuwien.ac.at> wrote:

> Hi Vladimir,
>
> since you have REed the raminit for Nehalem I'd like you to ask if you
> have any knowledge, information or pointers about using 8 GB DIMMs with
> it or even using more than 8 GB in total. In my case it is about an
> Arrandale i5-520M (in a Thinkpad 410s).
>
> I know that an i7-820QM (Clarksfield) is perfectly capable of working
> with 8 GB DIMMs and probably up to 32 GB or even more (the Thinkpad
> W510 has 4 DIMM slots and I have tested it with 20 GB) and that is from
> around the same time as the Arrendale chips - which does not mean
> anything but I still refuse to accept that Nehalem is that limited. The
> official specs are not trustworthy IMHO and cpuid(1) and /proc/cpuinfo
> show the same physical address width of 36 bits (which would indicate a
> maximum of 64 GB).
>
> The current raminit for Nehalem in coreboot is not able to train the two
> 8 GB DIMMs I have tested so far. I have added a debug output to
> choose_reg178 in the first loop before the margins are compared to
> STANDARD_MIN_MARGIN that shows that all margins are 0. If there is
> anything I could try or information I can provide, please let me know.
>
> The (ancient) vendor firmware I've been using on the T410s does
> sometimes manage to boot Linux with an 8 GB DIMM (dmesg is attached
> including the e820 map), but it is quite broken and memtest86 locks up
> or reboots within seconds so that's probably not a good target for RE
> efforts. :)
>
> --
> Kind regards/Mit freundlichen Grüßen, Stefan Tauner
>
> --
> coreboot mailing list: coreboot at coreboot.org
> https://www.coreboot.org/mailman/listinfo/coreboot
>
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