RISC-V CPUs with RVA23: More performance and better Linux support
64-bit processors with RISC-V instruction set according to RVA23 promise higher computing power for systems ranging from Android mobile devices to Linux servers.
(Image: c’t Magazin)
The members of the RISC-V Foundation have agreed on the new instruction set profile RVA23. Compared to older profiles such as RV64GC, it describes a greatly expanded mandatory functional scope of processor cores. There are also standardized equipment variants.
RVA23 thus promises significantly more powerful RISC-V processors as well as better software support, especially under Linux. This is because programmers now know exactly which functions are provided by RVA23-compatible RISC-V chips and can also expect a wider range of compatible processors and SoCs.
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The RISC-V profile RVA23 will also form the basis for an upcoming Android ABI for RISC-V. The RISC-V Foundation hopes that Android support will significantly boost growth for its open Instruction Set Architecture (ISA).
Extensive mandatory instruction set
Most Linux distributions for RISC-V have so far been designed for microprocessors with the RV64GC profile. In comparison, RVA23 cores are considerably more complex. The RISC-V Foundation lists vector instructions (V) and the hypervisor extension (H) for virtualization as the most important new features. In addition, RVA23 cores must also process a series of instructions that accelerate cryptographic algorithms.
The RISC-V Foundation has not yet been able to agree on SIMD extensions (P, Packed SIMD); however, a draft already exists.
RVA23 cores already on offer
The US company SiFive and the Taiwanese company Andes Technology are already selling RVA23-compatible CPU cores that chip developers can incorporate into their designs.
According to previous experience, however, it takes four to five years from the presentation of such an IP core (IP stands for Intellectual Property) until you can buy finished devices in which chips with these cores are used.
SiFive has the RVA23-compatible Performance P870-D on offer; the closely related P870 with RVA22 was already presented at the Hot Chips 2023 conference. The out-of-order core has a front end with six instruction decoders. The vector units process 128-bit vectors.
Depending on the production technology, the P870-D can achieve a clock frequency of around 3 GHz and can be used for chips with up to 256 CPU cores. The AndesCore AX66 from Andes Technology is somewhat weaker with four decoders.
(ciw)
