Condor's Cuzco RISC-V Core at Hot Chips 2025

Summary

Condor Computing, a subsidiary of Andes Technology that creates licensable RISC-V cores, has a business model with parallels to Arm (the company) and SiFive. Andes formed Condor in 2023, so Condor is a relatively young player on the RISC-V scene. However, Andes does have RISC-V design experience prior to Condor’s formation with a few RISC-V cores under their belt from years past.Condor is presenting their Cuzco core at Hot Chips 2025. This core is a heavyweight within the RISC-V scene, with wide out-of-order execution and a modern branch predictor and some new time based tricks. It’s in the same segment as high performance RISC-V designs like SiFive’s P870 and Veyron’s V1. Like those cores, Cuzco should stand head and shoulders above currently in-silicon RISC-V cores like Alibaba T-HEAD’s C910 and SiFive’s P550.Besides being a wide out-of-order design, Cuzco uses mostly static scheduling in the backend to save power and reduce complexity. Condor calls this a “time-based” scheduling scheme. I’ll cover more on this later, but it’s important to note that this is purely an implementation detail. It doesn’t require ISA modifications or special treatment from the compiler for optimal performance.Cuzco is a 8-wide out-of-order core with a 256 entry ROB and clock speed targets around 2 GHz SS (Slow-Slow) to 2.5 GHz (Typical-Typical) on TSMC’s 5nm process. The pipeline has 12 stages counting from instruction fetch to data cache access completion. However, a 10 cycle mispredict penalty probably more accurately describes the core’s pipeline length relative to its competitors.As a licensed core, Cuzco is meant to be highly configurable to widen its target market. The core is built from a variable number of execution slices. Customization options also include L2 TLB size, off-cluster bus widths, and L2/L3 capacity. Condor can also adjust the size of various internal core structures to meet customer performance requirements. Cuzco cores are arranged into clusters with up to eight...