nb/intel/sandybridge/raminit: Allow 933Mhz on Lenovo devices
Set max_mem_clock_mhz in devicetree to 933Mhz.
Allows to run the memory at up to DDR3-1866.
The same frequency was allowed within the first vendor bios,
but Lenovo than decided to limit it to DDR3-1333.
Tested on Lenovo T520 and DDR3-1600 DIMM (RMT3170eb86e9w16).
The RAM is now running at DDR3-1600 instead of DDR3-1333.
This gives about 4% performance increase in glmark2 using the
Intel GPU.
Change-Id: If15be497402d84a2778f0434b6381a64eda832d6
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/15158
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/mainboard/lenovo/t420/devicetree.cb b/src/mainboard/lenovo/t420/devicetree.cb
index 809e3ee..a921f76 100644
--- a/src/mainboard/lenovo/t420/devicetree.cb
+++ b/src/mainboard/lenovo/t420/devicetree.cb
@@ -18,6 +18,9 @@
register "gpu_cpu_backlight" = "0x1155"
register "gpu_pch_backlight" = "0x06100610"
+ # Override fuse bits that hard-code the value to 666 Mhz
+ register "max_mem_clock_mhz" = "933"
+
device cpu_cluster 0 on
chip cpu/intel/socket_rPGA988B
device lapic 0 on end