[coreboot] Sandybridge: native ram init

[Patrick Rudolph]

Hello,
I'm trying to get the GA-B75M-D3H to work, but I'm stuck at native ram
init.
It stops at "c320c discovery failed".
I figured out that the lower 4 lanes 0-3 are always erroneous in this
test.
The upper 4 lanes are working as expected and return errors depending on
the skew chosen. 
All previous tests work fine, so I guess it's not a hardware defect.
The PC boots using the stock UEFI.

Do you know a "good" RAM module/vendor that is known to work with this
board ?
I tested 
* Team Xtreme 2x 4GByte DDR3-2133
* Crucial 1x 2GByte DDR3-1600
but they show the same error message.

Do you have any further tips to debug this issue ?

Regards,
Patrick