Your original board supports:
"Supports up to Four 184-pin Direct Rambus RIMM modules up to 2GB (PC600/800)"
The replacement board:
http://support.intel.com/support/motherboards/desktop/d850md/
http://www.intel.com/support/motherboards/desktop/d850md/sb/cs-013277.htm
"What memory configurations are supported on the Intel® Desktop Board D850MD?
The Intel Desktop Board D850MD has two Dual RDRAM* channels supporting up to
two RIMMs* per channel (four total RIMM sockets). The Intel Desktop Board D850MD
can support memory configurations from 128 MB (minimum) to 2.0 GB (maximum)
utilizing 128 Mbit or 256 Mbit technology PC600 and PC800 compliant RDRAM RIMMs.
Note: PC700 RDRAM RIMM Memory can be installed. The BIOS will detect PC700 RDRAM
memory and will then default to a level of PC600 performance. RDRAM memory
configuration guidelines also apply to PC700 RDRAM RIMM memory. Refer to the
Intel Desktop Board D850MD Technical Product Specification (TPS) for more details"
http://www.intel.com/support/motherboards/desktop/d850md/sb/cs-013280.htm
The manual is here:
http://download.intel.com/support/motherboards/desktop/d850md/a6514501.pdf
I'd say that looks like a pretty close match. Presumably the "L" at the end
of the model name, means the optional LAN is present on the board.