Neptune is a 11 node Opteron Cluster.
It comprises of a head node and 10 compute nodes.
Overview
Each node has the following configuration

• Two AMD Opteron(248) 2.2 GHz processors
• 4 GB RAM
• 250 GB and 2 x 80 GB HD (Head node)
• 80 GB HD(compute nodes)
• Two Gigabit Ethernet ports

Interconnect: SMC 8524T 24 Port GigE switch.

Shown below is the picture of an individual compute node.

Microway Navion™ 1U Dual Opteron Chassis

*Microway,Navion are trademarks or registered trademarks of Microway, Inc.

Detailed Specifications:
Head node Configuration

• (2) AMD Opteron 248 with 1 MB L2 Cache
• (4) 1 GB DDR 400 MHz ECC/Reg Low Profile Memory
• (2) 80 GB Seagate Barracuda 7200.9 SATA II (3GB/s) 8MB Cache NCQ
  (OS Drives - Mirrored - RAID 1)

• 250 GB SATA II (3Gb/s) 7200 rpm w/16 MB cache Hard Drive
• Two Gigabit Ethernet ports
• Integrated 8MB ATI RAGE XL Graphics Controller

Compute nodes Configuration

• (2) AMD Opteron 248 with 1 MB L2 Cache
• (4) 1 GB DDR 400 MHz ECC/Reg Low Profile Memory
• 80 GB Seagate Barracuda 7200.9 SATA II (3GB/s) 8MB Cache NCQ
• Two Gigabit Ethernet ports