Hardware, Lenngren

Lenngren is a distributed memory computer form Dell consisting of 442 PowerEdge 1850 servers. Each node have two 3.4GHz "Nocona" Xeon processors and 8GB of main memory. The peak performance of the system is 6TFlop/s. The nodes are connected with gigabit ethernet for login and filesystem traffic. A high performance Infiniband network from Mellanox is used for MPI traffic.

Part of the machine is owned by two biochemistry groups at Stockholm University and KTH. There are just over 300 batch nodes available for general use.

Lenngren is named after Swedish 18th Century poet Anna Maria Lenngren.

Lenngren uses Intel Xeon processors with the EM64T extensions. EM64T stands for Extended Memory 64-bit Technology and is essentially a Intel-implementation of AMD's 64-bit extensions to the IA-32 (or x86) architecure called AMD64.

The major differences between EM64T/AMD64 and IA-32 are

• A 64-bit wide flat address space is supported
• The number of general purpose registers are increased from 8 to 16

  and their width is extended to 64 bits.

• The number of XMM registers (used by SSE) are increased from 8 to 16.
• The instruction set is expanded to take advantage of the new and wider registers.

InfiniBand is a bit-serial switched network with a raw data rate of 250MB/s in each direction per serial link. The nodes in the cluster use "4X" links which are four serial links run in parallel giving a peak data rate of 1GB/s in each direction. The InfiniBand adapters are connected to the system through a PCI-Express X8 slot which has a theoretical bandwidth of 2GB/s. Nodes are interconnected through a switch fabric that consists of 27 24-port switches, each connected to 16 nodes and with four uplinks each to two 120-port backbone switches.

The latency have been measured between two nodes that are on the same switch fabric.