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Andes adds to its Linux-ready RISC-V line-up with L2 and multi-core ready models

Dec 3, 2020 — by Eric Brown 4,278 views

Andes unveils four new Linux-focused RISC-V cores: The 32-bit A45MP and 64-bit AX45MP support up to 4x cores at up to 2.4GHz and offer optional L2 cache while the 32-bit A27L2 and AX27L2 also add optional L2.

Last December when Andes Technology announced its RISC-V architecture AndesCore 27-series of Linux-ready CPU cores, we somehow missed its announcement on the same day of more powerful 32- and 64-bit AndesCore 45-series cores. Now, the chip designer has added new models to both series.

The 32-bit A45MP and 64-bit AX45MP add multi-core support for up to quad-core designs to the 45-series and introduce optional L2 cache. The 32-bit A27L2 and AX27L2 also add optional L2 (see farther below).


A45MP and AX45MP

Like the earlier 45-series cores, the superscalar AndesCore A45MP and AX45MP are in-order, 8-stage dual-issue RISC-V processors. The 45-series also offers an optional DSP (RISC-V P-extension).

Like the A45 and AX45, but unlike the RTOS-focused D45, DX45, N45, and NX45 models, the new A45MP and AX45MP run Linux. They are equipped with a single or double precision Floating Point Unit and an MMU (Memory Management Unit). The earlier 45-series models became available in the third quarter and “have already been designed in by several customers,” says Andes.

The key to the multi-core support on the A45MP and AX45MP is a new directory-based Coherence Manager, which ensures cache coherence between Level-1 (L1) caches, the L2 cache, and cacheless bus masters. The Coherence Manager also helps deliver efficient transactions for shared memory accesses.

Compared to the 27-series, the A45MP and AX45MP provide 70 percent “total performance enhancement” with less than 50 percent additional logic area and dynamic power consumption, claims Andes. When using a 12nm process, the cores can achieve up to 2.4GHz clock frequency. The optional L2 cache controller helps meet the demands of applications like AR/VR, AI/ML, 5G, IVI, ADAS, video/image processing, enterprise-grade storage device, and networking.

A27L2 and AX27L2

Like the 32-bit A27 and 64-bit AX27 and the earlier A25 and AX25, the new 32-bit A27L2 and 64-bit AX27L2 support Linux. These AndesCore designs inherit the MemBoost feature from the earlier 27-series processors, enabling “multiple outstanding data accesses and I/D cache prefetch to greatly boost the memory subsystem performance with higher bandwidth and lower access latencies,” says Andes.

AX27L2 block diagram, which is the same as the A27L2 diagram
(click image to enlarge)

They key addition is the new L2 cache controller, which raises memory bandwidth by 2x and reduce memory latencies by 70 percent, claims Andes. Aside from the 32-bit/64-bit difference, the processors appear to be identical, with the same block diagram features. They continue to be limited to single-core designs.

Other features include a 5-stage pipeline, a DSP/SIMD ISA, branch prediction, an MMU, and more. The A27L2 supports up to 3.58 Coremark/MHz and 1.96 DMIPS/MHz and the AX27L2 supports 3.52 Coremark/MHz and 2.09 DMIPS/MHz.

Firmware and software support

All the new 45-series and 27-series cores support the Andes V5 architecture and are compliant with updated RISC-V extensions. Andes V5 features include PowerBrake, QuickNap, and WFI for additional power saving. The architecture also provides StackSafe for stack overflow/underflow protection and CoDense for additional code density enhancement on top of the RISC-V C-extension.

The A45MP/AX45MP and A27L2/AX27L2 cores are supported by Andes development tools such as AndeSight IDE and Andes Custom Extension framework. They are compatible with RISC-V ecosystem solutions including security, system level modeling, and hardware debug/trace subsystems.

In other recent RISC-V news, Micro Magic announced an up to 64-bit RISC-V core boasting a groundbreaking 110,000 CoreMarks/Watt, with a 3GHz chip consuming less than 70mW. The company claims 10 times better CoreMarks/Watt compared to other processors in the 3-5GHz range.

Further information

No production timetable was listed for the AndesCore A45MP/AX45MP and AndesCore A27L2/AX27L2 cores. More information may be found in Andes Technology’s joint announcement. Andes currently has product pages only for the A27L2 and AX27L2.

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