SiFive unveils P870 high-performance core, discusses future of RISC-V

SiFive Hot Chips 2023 x86 vs Arm vs RISC-V
Comparing ISA Business Models – x86 vs Arm vs RISC-C – Source: 果壳 (Guokr)

SiFive has just given a presentation at Hot Chips 2023 introducing the new high-performance P870 RISC-V core and its automotive equivalent the P870-A core, plus discussing RISC-V in general, its previous generation RISC-V cores, and what to expect going forward.

SiFive has not officially announced the P870 and P870-A cores just yet, so most of the information we have from the English-speaking Internet is from ServeTheHome who managed to get some presentation slides, but this is also corroborated by various Chinese sources on Baidu and Guokr.

SiFive P870 and P870-A

SiFive P870 and P870-A

The P870 and P870-A RISC-V cores are new cores from the SiFive Performance family compatible with the RISC-V RVA23 profile and succeeding the SiFive P670 core. The SpecINT2k6 benchmark reports 17 points per GHz on the P870 compared to 13.2 points per GHz for the P670 (comparable to the Arm Cortex-A78) or about a 29% higher performance at the same frequency.

SiFive P870 P670 P470 X280 SoC

The SiFive P870 should be found in heterogonous SoCs with P670 and P470 cores, with each cluster using shared L2 cache, and potentially combined with multiple Intelligence X280 AI accelerators in data center chips.

P870 microarchitecture

The P870 microarchitecture diagram shows the out-of-order processor comes with 64KB I-cache, a 6-issue out-of-order pipeline, an FPU unit, vector extensions as well as L2 cache (shared per cluster) and shared L3 cache.

The diagram below shows what a 32-core P870 processor would look like and how the cache is distributed.

32-core RISC-V processor with L2 & L3 cache

This is what a consumer RISC-V SoC based on the new core could look like with two P870 performance cores, four P470 efficiency cores, and an always-on E6 core, plus some other IP blocks such as WorldGuard security.

Consumer RISC-V SoC

The P870-A is basically the same as the P870 plus functional safety (FuSa) features such as lockstep support, ECC cache, and an advanced RAS architecture. You’ll find more slides about P870 and P870-A in the aforelinked article published on ServeTheHome website.

The future of RISC-V and SiFive CPU

SiFive also discussed the future prospects of RISC-V and other upcoming CPUs from the company. Sales of RISC-V cores have really started to pick up in 2023, but are expected to go ballistic in 2024 and 2025 with a conservative estimate of 80 billion RISC-cores shipped in products by 2025.

RISC-V Growth

SiFive claims to have over 100 customers including 8 of the top 10 semiconductor vendors, so many more RISC-V processors should be introduced to the market in the next few years from well-known names, and Intel, Qualcomm, SK Hynix, Western Digital, and others are investors in the company.

SiFive Customers

They also briefly mentioned the situation between SiFive and StarFive which started as a reseller of SiFive IP cores in China but is now its own independent entity with different products.

SiFive StarFive

While the P870 and P870-A cores should become available in 2024, the company also teased the Napa RISC-V Performance core to be launched in 2025, but we do not have any details so far.

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