Preface: AMD 7000 series (7-series) processors are extensively used to build High Performance Clusters (HPC). AMD provides 7-series solutions for both enterprise-grade and consumer/prosumer levels:

• AMD EPYC™ 7002 and 7003 Series: These server-grade processors (codenamed “Rome” and “Milan”) are specifically designed for commercial and scientific HPC. They offer up to 64 cores per socket, high memory bandwidth (8 channels), and extensive PCIe Gen4 lanes to reduce data bottlenecks.
• AMD Ryzen™ 7000 Series: While typically consumer CPUs, they are often used for “personal HPC” or small-scale clusters due to their high clock speeds and performance-per-dollar for specialized parallel computing tasks.

Background: The “Readback CRC Bus” refers to the internal logic path or mechanism in FPGAs (especially AMD/Xilinx devices) used to perform readback cyclic redundancy checks.

This is not a physical external “bus,” but a key component of the configuration logic, primarily used to ensure the data integrity of the FPGA’s internal configuration memory. Its core functions.

Academic studies and AMD’s bulletin describe attacks where researchers collect near‑infrared photon emissions that escape from transistor switching events on the FPGA die.

This depends on silicon’s bandgap (~1.1 eV ⇒ transparent above ~1100 nm). Because of this:

• Visible light cannot pass through silicon.
• Near‑IR and SWIR (1.1–2.3 µm) passes through with relatively low attenuation.
• The plastic/epoxy package is often more opaque, so attacking from the backside of a thinned die is normal.

The reason backside emissions are detectable:

• switching transistors emit very weak photons,
• silicon becomes transparent above ~1100 nm,
• the backside offers a direct path to the active circuitry after thinning,
• the metallization layers on the front side block light.

This is the same principle used in IRIS inspection methods, which also rely on silicon’s IR transparency for imaging.

Technical Summary: By leveraging a physical optical side channel, an attacker could recover plaintext configuration data from encrypted bitstreams. AMD recommends maintaining good physical security practices and keeping  systems closed unless needed for maintenance and repairs by authorized personnel.

 Affected Products and Mitigation: The testing by the academics was done on AMD Xilinx 7 series FPGAs. This is a physical back side attack and is outside of the threat model for AMD 7-series FPGAs.

Official announcement: Please refer to the link for more details – https://www.amd.com/en/resources/product-security/bulletin/amd-sb-8022.html