HP ROM-Based Setup Utility - Manual (Page 143)

Memory Speed with 2 DIMMs per Channel
NOTE: This option is available on G7 servers with Intel 5500-series processors.
This option configures the system to run DIMMs at 1333 MHz when up to two DIMMs are installed
on a memory channel, if all other requirements for 1333 MHz operation are met. This provides a
performance increase for most workloads. By default, the system will operate at a maximum 1066
MHz when two DIMMs are installed on any memory channel. HP has validated this functionality
with all HP DIMMs.
HP recommends that this setting remain at the default of 1066 MHz maximum when using DIMMs
not manufactured by HP.
Advanced Options menu 143