1 Specification
2 Important Properties
- 2.1 SMT (aka. Hyperthreading)
- 2.2 Instruction Set
- 2.3 NUMA-Domains
- 2.4 Topology

The compute nodes, fpga nodes and gpu nodes of Noctua 2 have dual-socket AMD EPYC Milan CPUs.

Specification

The specification is as follows

Property	normal, largemem, gpu	hugemem, fpga-nodes

Property	normal, largemem, gpu	hugemem, fpga-nodes
CPUs	2xAMD EPYC Milan 7763	2xAMD EPYC Milan 7713
Microarchitecture	Zen3	Zen3
Cores per node in total	128	128
Cores per socket	64	64
Sockets per node	2	2
SMT	off	off
L3 Cache per socket	256 MB	256 MB
TDP per socket	280 W	225 W
Base frequency	2.45 GHz	2.0 GHz
Max. Boost frequency	3.5 GHz	3.675 GHz
Main memory	256/1024/512 GB DDR4 3200 MHz	2048/512 GB DDR4 3200 MHz
Memory channel per socket	8	8
Memory bandwidth (Stream triad)	~370 GB/s	~370 GB/s
Floating-Point Peformance (single-node HPL)	~ 4.0 TFLOP/s	~ 3.7 TFLOP/s
Floating-Point Peformance (single-node HPCG)	~ 62 GFLOP/s	~ 62 GFLOP/s

Important Properties

SMT (aka. Hyperthreading)

SMT is disabled on Noctua 2.

Instruction Set

The AMD Milan (Zen3) CPUs can do up to 256-bit SIMD, i.e. AVX2.

NUMA-Domains

The CPUs run in the NPS=4 mode. That means that there are 4 NUMA domains per socket so in total a single node has 8 NUMA domains.

Topology

The basic unit of an AMD EPYC Milan CPU is a CCD (Core Compute Die) with 8 CPU cores and 32 MB of L3-Cache. In the above-mentioned NPS=4-configuration two such CCDs mark up a NUMA domain and 4 NUMA domains are on one socket.

Noctua 2 CPU architecture with 2 AMD EPYC Milan CPU sockets

Thus, we recommend using chunks of 8 cores, e.g. a calculation with 32 cores that uses 4 tasks (MPI ranks) and 8 threads per task.

The layout of a compute node depicted below. For other node types see