Alps (supercomputer)

To suitably house and operate modern supercomputers, a new data center building and an adjacent office building were constructed in Lugano-Cornadero. The data center building consists of three floors. The lowest floor houses the basic infrastructure with primary power and water distribution as well as an emergency power supply via batteries. The cooling of the computers and the buildings in summer is done with lake water from Lake Lugano. From a depth of 45 meters, 460 liters of cold lake water per second are supplied to the data center via 2.8 km long pipes. There, it cools the internal cooling circuit of the computer via a heat exchanger.^[6] The secondary distribution is done on the middle floor using power distribution units, which allow flexible installation of the computers above. The computers are located on the top floor.^[7] The latest Alps highly-parallel supercomputer was delivered by Hewlett Packard Enterprise (HPE), which acquired the supercomputer-specialized company Cray as a subsidiary in 2019. It is installed on an area of 2000 m². The total cost was about 100 million CHF.

In order to achieve superior performance, combinations of central processors (CPUs) with graphics processors (GPUs) as well as their associated memories (128 GB LPDDR-5X RAM; 96 GB HBM-3)^[8] are placed in close proximity on the same monolithic integrated circuit provided by Nvidia. Arrays of 72 CPUs are called Grace and consist of ARMv9-Neoverse-V2 processors, which are RISC processors. The 132 GPUs are called Hopper H100 Tensor Core.^[9] The combinations of said 72 CPUs together with 132 GPUs integrated on a VLSI chip are called GH200 Grace Hopper in memory of Grace Hopper. A total of 1'305'600 processor cores (CPUs and GPUs) are available on this Alps system. Data exchanges between the 2'688 nodes occur on an Ethernet-type network called Slingshot-11 at a rate of 200 Gbit/s.^[10][8] A single node is composed of four GH200, in a Quad GH200 configuration. Every Quad GH200 node acts as a single NUMA system, with 288 CPU cores and 4 GPUs. The Grace CPUs communicate through a cache-coherent interconnect, while the Hopper GPUs communicate through NVLink.^[11]

A team from CSCS develops special software for different applications. The power consumption of the computer at full load is 10 MW. The electricity costs are estimated to be around 15 million CHF per year.