AMD CPU slurm guide for Eiger.Alps (#167)

* how to use slurm on zen2 nodes
* general hardware information about zen2 nodes

Author: bcumming

docs/alps/hardware.md

@@ -3,8 +3,8 @@
 
 Alps is a HPE Cray EX3000 system, a liquid cooled blade-based, high-density system.
 
-!!! todo
-    this is a skeleton - all of the details need to be filled in
+!!! under-construction
+    This page is a work in progress - contact us if you want us to prioritise documentation specific information that would be useful for your work.
 
 ## Alps Cabinets
 
@@ -40,13 +40,13 @@ Alps was installed in phases, starting with the installation of 1024 AMD Rome du
 
 There are currently five node types in Alps:
 
-| type           | abbreviation  | blades | nodes | CPU sockets | GPU devices |
-| ----           | -------       | ------:| -----:| -----------:| -----------:|
-| NVIDIA GH200   | gh200         | 1344   | 2688  | 10,752      | 10,752      |
-| AMD Rome       | zen2          |  256   | 1024  |  2,048      | --          |
-| NVIDIA A100    | a100          |   72   |  144  |    144      | 576         |
-| AMD MI250x     | mi200         |   12   |   24  |     24      |  96         |
-| AMD MI300A     | mi300         |   64   |  128  |    512      | 512         |
+| type                                | abbreviation  | blades | nodes | CPU sockets | GPU devices |
+| ----                                | -------       | ------:| -----:| -----------:| -----------:|
+| [NVIDIA GH200][ref-alps-gh200-node] | gh200         | 1344   | 2688  | 10,752      | 10,752      |
+| [AMD Rome][ref-alps-zen2-node]      | zen2          |  256   | 1024  |  2,048      | --          |
+| [NVIDIA A100][ref-alps-a100-node]   | a100          |   72   |  144  |    144      | 576         |
+| [AMD MI250x][ref-alps-mi200-node]   | mi200         |   12   |   24  |     24      |  96         |
+| [AMD MI300A][ref-alps-mi300-node]   | mi300         |   64   |  128  |    512      | 512         |
 
 [](){#ref-alps-gh200-node}
 ### NVIDIA GH200 GPU Nodes
@@ -81,16 +81,44 @@ Each node contains four Grace-Hopper modules and four corresponding network inte
 [](){#ref-alps-zen2-node}
 ### AMD Rome CPU Nodes
 
-!!! todo
+These nodes have two [AMD Epyc 7742](https://en.wikichip.org/wiki/amd/epyc/7742) 64-core CPU sockets, and are used primarily for the [Eiger][ref-cluster-eiger] system. They come in two memory configurations:
+
+* *Standard-memory*:  256 GB in 16x16 GB DDR4 DIMMs.
+* *Large-memory*:  512 GB in 16x32 GB DDR4 DIMMs.
+
+!!! note "Not all memory is available"
+    The total memory available to jobs on the nodes is roughly 245 GB and 497 GB on the standard and large memory nodes respectively.
+
+    The amount of memory available to your job also depends on the number of MPI ranks per node -- each MPI rank has a memory overhead.
+
+A schematic of a *standard memory node* below illustrates the CPU cores and [NUMA nodes](https://www.kernel.org/doc/html/v4.18/vm/numa.html).(1)
+{.annotate}
 
-EX425
+1. Obtained with the command `lstopo --no-caches --no-io --no-legend eiger-topo.png` on Eiger.
+
+![Screenshot](../images/slurm/eiger-topo.png)
+
+* The two sockets are labelled Package L#0 and Package L#1.
+* Each socket has 4 NUMA nodes, with 16 cores each, for a total of 64 cores per socket.
+
+Each core supports [simultaneous multi threading (SMT)](https://www.amd.com/en/blogs/2025/simultaneous-multithreading-driving-performance-a.html), whereby each core can execute two threads concurrently, which are presented as two processing units (PU) per physical core:
+
+* the first PU on each core are numbered 0:63 on socket 0, and 64:127 on socket 1;
+* the second PU on each core are numbered 128:191 on socket 0, and 192:256 on socket 1;
+* hence, core `n` has PUs `n` and `n+128`.
+
+Each node has two Slingshot 11 network interface cards (NICs), which are not illustrated on the diagram.
 
 [](){#ref-alps-a100-node}
 ### NVIDIA A100 GPU Nodes
 
-!!! todo
+The Grizzly Peak blades contain two nodes, where each node has:
 
-Grizzly Peak
+* One 64-core Zen3 CPU socket
+* 512 GB DDR4 Memory
+* 4 NVIDIA A100 GPUs with 80 GB HBM3 memory each
+    * The MCH system is the same, except the A100 have 96 GB of memory.
+* 4 NICs -- one per GPU.
 
 [](){#ref-alps-mi200-node}
 ### AMD MI250x GPU Nodes