New RISC-V processor family

From microcontroller to multicore processor

10. November 2021, 11:30 Uhr | By Frank Riemenschneider, Segger Microcontroller

Fortsetzung des Artikels von Teil 2

SiFive vs. Arm

The U74 competes directly with Arm's Cortex-A55. The U74 and A55 both have an eight-stage in-order dual-issue pipeline, with SiFive's design achieving about 11 % more CoreMarks/MHz. The U74 also comes out ahead in power and area efficiency. On the other hand, the A55 includes an FPU that handles neon single instruction multiple data (SIMD) vector instructions.

The E76 is comparable to Arm's Cortex-M7 in terms of integer performance. Both are dual-issue microcontrollers that deliver about 5.0 CoreMarks/MHz, with the Arm microcontroller having a slight edge. The Cortex-M7 includes DSP/SIMD enhancements that the E76 does not; both manufacturers offer optional FPUs. Although the E76 doesn't quite match the M7 for power efficiency, it achieves a higher clock speed of up to 1.6 GHz in the same manufacturing process.

The S76 does not have a 64-bit competitor from Arm. The Cortex-R8 is similar, but it is a 32-bit processor and does not come close to the S76 in the Coremark benchmark.

SiFive and Arm's offerings also differ in their multicore configurations. The 7-series has a shared L2 cache. In contrast, the Cortex-A55 has a private L2 cache and a shared L3 cluster cache, while the Cortex-M and Cortex-R CPUs do not support private L2 caches.

The agony of choice – Segger supports them all

As always, which choice is best depends on the application. SiFive's 7-series delivers an impressive 63 % performance increase over the 5-series. More importantly, it allows SiFive to compete against dual-issue Arm CPUs such as Cortex-M7 and Cortex-A55. The increased performance of the U74 also expands the range of Linux applications that RISC-V can serve. To compete with Arm in applications that require DSP or AI processing, SiFive had to add a vector unit: Although there is a VIS7 announcement on this (see box: Vector Unit for S7 from SiFive), the product is not officially offered on SiFive's website at this time.

Regardless of whether a processor from Arm or SiFive is chosen, for debugging Segger offers a uniform tool with the J-Link [1]. It was voted the best debugger by electronics readers in a survey [2]. Segger's Embedded Studio IDE, which scored excellently in the last Elektronik reader test, is also available for Arm and RISC-V [3]. And last but not least embOS for RISC-V, the preferred RTOS choice for engineers all over the world, offers incomparable ease-of-use and guarantees 100 % deterministic real-time operation for any embedded RISC-V device.  Certified by TÜV SÜD, embOS complies with the functional safety standards IEC 61508 SIL 3 and IEC 62304 Class C. More technical details you can find at Segger's Platform for RISC-V overview [4].

References:

[1] SEGGER's J-Link debugging tools for SiFive and Arm CPUs: https://www.segger.com/products/debug-probes/j-link/

[2] Schlichtmeier, T.: Reader survey on debugging - These are the top 3. elektronik.de, May 25, 2021, www.elektroniknet.de/embedded/entwicklungstools/das-sind-die-top-3.186641.html

[3] Stelzer, G.: »Embedded Studio« from Segger with top rating. Electronics 2021, H. 4, pp. 6-9.

[4] SEGGER’s RISC-V platform: https://www.segger.com/risc-v/

Frank Riemenschneider von Segger Microcontroller
Frank Riemenschneider is Senior Marketing- and Public Relations Manager at Segger Microcontroller.
© Segger Microcontroller

The author:


Frank Riemenschneider from Segger Microcontroller studied electrical engineering at the Leibniz University of Hanover with a focus on processor architectures. He joined Segger Microcontroller in March 2021 as Senior Marketing- and PR Manager, overseeing the entire product line.
frank.riemenschneider@segger.com


  1. From microcontroller to multicore processor
  2. New CPU in Series 7
  3. SiFive vs. Arm

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