AMD crafts custom EPYC CPU with HBM3 memory for Microsoft Azure – CPU with 88 Zen 4 cores and 450GB of HBM3 may be repurposed MI300C, four chips hit 7 TB/s

Microsoft announced its latest high performance computing (HPC) Azure virtual machines powered by a custom AMD CPU that may have once been called MI300C.

The HBv series of Azure VMs are focused on delivering high amounts of memory bandwidth, an important specification for HPC; Microsoft calls it the “biggest HPC bottleneck.” Previously, Microsoft had used Milan-X and Genoa-X server CPUs with AMD’s 3D V-Cache to provide this extra bandwidth, but for the latest HBv5 VMs, Microsoft clearly wanted something even more performant.

The custom AMD CPU used for HBv5 VMs leverages HBM3, usually the memory of choice for the latest data center-class GPUs, such as AMD’s MI300X. With a bandwidth of 6.9TB/s from four of the chips in a single VM, the VMs are almost nine times faster than the Genoa-X CPUs that Microsoft offers in HBv4 VMs, and nearly 20 times faster than Milan-X chips in HBv3 VMs.

When paired with a CPU, the HBM3 fulfills a similar role as 3D V-Cache. Still, instead of expanding the pool of L3 cache, it effectively adds a massive L4 cache with even greater bandwidth and presumably much worse latency. However, the latter isn't as important in certain types of workloads.

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