AndesCore™ AX25

Compact High-Speed 64-bit CPU for Real-time and Linux Applications

AndesCore™ AX25 Overview

  • AndeStar™ V5 Instruction Set Architecture (ISA), compliant to RISC-V technology
  • DSP/SIMD ISA to boost the performance of digital signal processing
  • Floating point extension
  • Bit-manipulation extensions
  • Andes extensions, architected for performance and functionality enhancements
  • Separately licensable Andes Custom Extension™ (ACE) for customized acceleration
  • 64-bit CPU architecture, enabling software to utilize the memory spaces far beyond 4G bytes imposed by 32-bit CPUs
  • 16/32-bit mixable instruction format for compacting code density
  • Branch prediction to speed up control code
  • Return Address Stack (RAS) to speed up procedure returns
  • Memory Management Unit (MMU) and Physical Memory Protection (PMP)
  • Flexibly configurable Platform-Level Interrupt Controller (PLIC) for supporting wide range of system event scenarios
  • Enhancement of vectored interrupt handling for real-time performance
  • Advanced CoDense™ technology to reduce program code size

AndesCore™ AX25 is a compact 64-bit CPU IP core based on AndeStar™ V5 architecture which incorporated RISC-V technology, it is tailored for high-performance embedded applications that needs to access address space over 4GB. AX25 also supports the RISC-V P-extension (draft) DSP/SIMD ISA contributed by Andes, single- and double-precision floating point and bit-manipulation instructions, and MMU for Linux based applications. AX25 comes with options, including branch prediction for efficient branch execution, Instruction and Data caches, Local Memories for low-latency accesses, ECC for L1 memory soft error protection, and Andes Custom Extension™ (ACE) to add proprietary instructions to accelerate performance/power consumption critical spots.

AX25’s 5-stage pipeline is optimized for high operating frequency and high performance. Features also includes PLIC and vectored interrupts for serving various types of system events, AXI or AHB 64-bit data bus for addressing up to 64-bit address, PowerBrake, QuickNap™ and WFI mode for low power and power management, and JTAG debug interface for development support.

Applications

  • Video processing
  • Smart wireless switch/router
  • Computer Vision and Pattern Recognition
  • Machine/Deep Learning acceleration

Block Diagram

Development Tools

  • AndeSight™ Integrated Development Environment
  • COPILOT: Custom-OPtimized Instruction deveLOpment Tool for ACE
  • ICE debugging hardware

Key Features and Performance

AndeStar™ V5 Architecture

Key FeaturesBenefits
RISC-V RV64IMACFDBP instructions
  • State-of-the art ISA from latest developments in computer architecture
  • Industry standard and open architecture
64-bit CPU architectureEnabling software to utilize the memory spaces far beyond the 4G byte limit of 32-bit CPUs
RISC-V P-extension (draft) DSP/SIMD instructions with versatile operationsBoost the performance of voice, audio, image and signal processing
RISC-V single and double precision floating point instructionAccelerate the processing of high precision arithmetic
RISC-V bit-manipulation instructions, including the Zba, Zbb, Zbc and Zbs extensionsBenefits codes with bit-wise operations
Andes Extended InstructionsAndes exclusive performance and functionality enhancements
Andes Custom Extension™ (ACE) option to create customized instructions for software acceleration
  • Add customized instruction extensions to facilitate Domain-Specific Architecture/Acceleration (DSA)
  • Boost application performance significantly, at the same time maintain the programmability
  • Powerful constructs are available to define high level instruction
  • ACE design is based on Verilog and C languages which are familiar to the designers
  • The COPILOT tool automatically generates the extended CPU and software toolchain
  • Do not require expertise in processor pipeline to design ACE instructions
16/32-bit mixable instruction formatFor compact code density
32 general-purpose registersFor better code size and performance
Machine (M), User (U) and Supervisor (S) Privilege levelsFor Linux and advanced operating systems with protection between kernel and user programs

CPU Core

Key FeaturesBenefits
3.55 Coremark/MHz, 2.14 DMIPS/MHz*Superior performance-per-MHz
5-stage pipeline, with a full-cycle reserved for critical SRAM accessesSuperior performance-efficiency, while allowing for high speeds

Extensive branch prediction features

  • Branch Target Buffer (BTB): 32, 64, 128 or 256-entry
  • Branch History Table (BHT): 256-entry, with 8-bit branch history
  • Return Address Stack (RAS): 4-entry
  • Branch Target Buffer and Branch History Table to speed up control codes
  • Return Address Stack to speeds up procedure returns

Memory Management Unit

  • Sv39, Sv48 virtual-memory systems
  • 4/8-entry fully associative ITLB/DTLB
  • 32/64/128-entry 4-way set-associative shared TLB
  • Hardware page table walker
  • Virtual memory support for full address space and easy code/data sharing
  • Support for full-featured OS such as Linux
  • Protection of supervisor and user privilege
  • Hardware for fast address translation
Physical Memory Protection (PMP), 16 regionsBasic read/write/execute memory protection with minimum cost
Performance monitorsProgram code performance tuning
StackSafe™ hardware stack protection
  • Easy identification of stack size threshold during development
  • Hardware error detection of stack overflow and underflow at runtime

Multiplier options

  • Fast multiplier: pipelined, 2-cycle
  • Small multipliers: producing 1, 2, 4, or 8 bits per cycle
Option to choose between speed and area according to application's requirements
PowerBrake technologyPerformance throttling to digitally reduce power consumption
QuickNap™ technologyFast power-down/wake-up support for caches

* AndeSight v500, DMIPS/MHZ follow Dhrystone’s no-inline ground rules, best performances

Memory Subsystems

Key FeaturesBenefits

I-Cache & D-Cache

  • Size: 4KB to 64KB
  • Set associativity: Direct-mapped, 2-way or 4-way
  • Accelerating accesses to slow memories
  • Flexible cache configurations

ILM & DLM

  • Size: 4KB to 16MB
  • SRAM or AHB-Lite interface support
  • Bus masters accesses by AHB slave port
  • For deterministic and efficient program execution
  • Flexible size selection to fit diversified needs
Soft-error protection: ECC or parity for I-Cache and D-Cache, ILM and DLM with SRAM interfaceCode and data integrity protection
Bus master port: AHB or AXI with 64-bit data, 32 to 64-bit address, AXI with I/D separate or joint busUser-selectable bus interface for optimal efficiency
Bus save port: AHB with 64-bit data, for ILM/DLM accesses Efficient data transfer between CPU and SoC masters
Core/bus clock ratio of N:1Simplified SoC integration

Platform-Level Interrupt Controller (PLIC)

Key FeaturesBenefits

Implements RISC-V PLIC specification

  • Up to 1023 PLIC interrupt sources
  • Up to 255 PLIC interrupt priority levels
  • Up to 16 PLIC interrupt targets
Allow individual interrupts to be serviced and prioritized without sharing

Enhanced interrupt features

  • Vectored interrupt dispatch
  • Priority-based preemption
  • Selectable edge trigger or level trigger
  • Faster interrupt handling for real-time applications
  • Complete hardware preemption support for faster response
  • Flexible interrupt source interface for simpler SoC design

Debug Support

Key FeaturesBenefits
Implements RISC-V debug specificationsSupported by industry debug tool suppliers
JTAG Debug PortIndustry-standard support
Embedded Debug Module with up to 8 triggersFlexible configurations to tradeoff between gate count and debugging capabilities
Exception redirection supportEntering debugger upon selected exceptions without using breakpoints

Performance

Core, Process AX25 (w/o DSP, FPU), 28HPC+ AX25 (with DSP, FPU), 28HPC+
Frequency (MHz)10001000
Dynamic power (uW/MHz)2022
Area (mm2)0.1110.209

* Configured with cache and MMU. SVT 9-track library, SS corner, 0.81V, -40°C, and with I/O constraint. Power consumption at TT corner, 0.9V, 25°C

Product Package

AX25 with AE350 Platform