Arm adds configurable Neoverse CSS N4 alongside AGI CPU

Arm introduced Neoverse CSS N4 on September 8 as a configurable compute subsystem for partners building custom data-center silicon. Customers now have two Arm-based paths: configure a specialized processor around CSS N4 or deploy the company’s complete AGI CPU.

CSS N4 combines Neoverse N4 CPU cores with pre-integrated system IP, software and reference designs. Arm’s product page says partners can adjust core count, cache, memory, I/O, accelerator attachment and chiplet connectivity. Arm supplies the subsystem as register-transfer-level, or RTL, design code for electronic design automation tools, with implementation guidance and software for Linux boot and validation.

Arm lists configurations from 8 to 128 cores per die, frequencies up to 3.8 GHz, LPDDR6 memory support and PCIe Gen 7. The company says CSS N4 delivers up to twice the performance per socket, 1.25 times the performance per watt and 1.75 times the memory bandwidth of CSS N3. Arm has not disclosed the benchmark workloads, full configurations or testing method behind those comparisons, and the reviewed sources contain no independently run CSS N4 benchmark.

The company says CSS N4 is intended for cloud, networking and AI infrastructure, including scale-out computing, web services, cloud-native workloads, agentic AI and data processing units. For context on a different layer of the infrastructure stack, DataPhoenix has covered a software-layer approach to AI inference infrastructure.

Arm announced the AGI CPU on March 24 as its first Arm-designed data-center CPU and the start of its move into production silicon products. In September, Arm described the AGI CPU as a production-ready option for customers that do not need custom silicon and CSS N4 as the configurable foundation for companies that do. Arm has not identified a CSS N4 silicon customer or disclosed a tape-out or general-availability date.