Makes it tought when the symptoms don't really make any sense. Setting an RMM3 to DHCP should have zero impact on the systems ability to boot.
CMOS corrupted. Try clearing CMOS http://download.intel.com/support/motherboards/server/s3420gp/sb/sr1695gprx_tps_r1_5.pdf page 58
On BIOS recovery,
A few hints which are well buried in the documentation.
1) You need a DOS bootable USB keyfob. ( the system will boot to EFI , but for some reason it looks for a bootable partition)
2) You need to extract the code package to the root directory of the key fob. http://downloadcenter.intel.com/confirm.aspx?httpDown=http://downloadmirror.intel.com/20220/eng/S3420GPLXLC_EFI_BIOS49_BMC124_FRUSDR20.zip&lang=eng&Dwnldid=20220&DownloadType=Firmware&OSFullname=OS+Independent
These files are required to be in the root:
- and a startup.nsh (which needs to be edited to just contain the line: iFlashx64 R0049REC.CAP /u )
3) Set the recovery jumper
4) Power -up and take a break. It takes a LOOOOOOONG time to complete. ( give it 10 minutes or more)