AndesCore™ AX45

AndesCore™ AX45 Overview

  • 64-bit in-order dual-issue 8-stage pipeline CPU architecture
  • AndeStar™ V5 Instruction Set Architecture (ISA), compliant to RISC-V technology
  • DSP/SIMD extensions
  • Floating point extensions
  • Andes extensions, architected for performance and functionality enhancements
  • 16/32-bit mixable instruction format for compacting code density
  • Advanced low power branch predication to speed up control code
  • Return Address Stack (RAS) to accelerate procedure returns
  • Memory Management Unit (MMU), Physical Memory Protection(PMP), and programmable Physical Memory Attribute (PMA)
  • MemBoost for heavy memory transactions
  • 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

The 64-bit AX45 is an 8-stage superscalar processor that supports RISC-V specification, including “G” (“IMAFD”) standard instructions, “C” 16-bit compression instructions, “P” Packed-SIMD/DSP instructions, “N” for user-level interrupts and Memory Management Unit (MMU) for Linux support. It issues two instructions per cycle that significantly increases the performance efficiency that is important for many applications. AX45 is also equipped with comprehensive SIMD/DSP instructions that can boost the performance of voice, audio, image and signal processing. Its “FD” extensions support IEEE754-compliance single and double precision floating point instructions as well. It incorporates MemBoost to greatly enhance memory bandwidth and reduce memory latencies for applications with intensive memory accesses. In addition, AX45 features advanced low power branch prediction mechanism for efficient branch execution, instruction and data caches, local memories, and ECC error protection. It also includes vectored and preemptive interrupt controller to serve diversified system events, AXI 64-bit bus, rich power management, and JTAG debug and trace interface for software development support.


  • Linux Operating System Based Applications
  • AR/VR
  • Networking and Communications
  • Video and Image Processing
  • Machine/Deep Learning acceleration
  • Advanced High Capacity storage

Block Diagram

Development Tools

  • AndeSight™ IDE (Eclipse-based)
    • Compiler, Debugger, Profiler, Register Bit-field Display/Update, RTOS Awareness, and more
    • Tested platforms: Windows and Linux , single- or multi-user installation
  • Andes BSP
    • Optimized DSP library
    • Demo examples and sample projects
  • RTOSes
    • Open-source: FreeRTOS, Zephyr, RT-Thread
    • Commercial: μC/OS-II, ThreadX,
  • Linux kernel and platform drivers
  • FPGA Development Boards
    • AndeShape™ ADP-XC7 (full-featured)
  • Debugging Hardware

Key Features and Performance

AndeStar™ V5 Architecture

Key FeaturesBenefits
  • State-of-the art ISA from latest developments in computer architecture
  • Industry standard and open architecture
RISC-V P-extension (draft) DSP/SIMD instructions with versatile operations Boost the performance of voice, audio, image and signal processing
RISC-V single and double precision floating point instruction Accelerate the processing of high precision arithmetic
Andes Extended Instructions Andes exclusive performance and functionality enhancements
16/32-bit mixable instruction format For compact code density
32 general-purpose registers For better code size and performance
Machine (M), User (U) and Supervisor (S) Privilege levels For Linux and advanced operating systems with protection between kernel and user programs

CPU Core

Key FeaturesBenefits
5.50 Coremark/MHz, 3.14 DMIPS/MHz* Excellent performance-per-MHz
8-stage dual-issue in-order pipeline Superior performance-efficiency, while allowing for high speeds

Extensive branch predication features

  • Branch Target Buffer (BTB)
  • Branch History Table (BHT)
  • Return Address Stack (RAS)
  • 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 ITLB/DTLB
  • Up to 512-entry shared TLB
  • 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 regions Basic read/write/execute memory protection with minimum cost
Programmable Physical Memory Attribute (PMA), 16 regions

Configurable memory attributes:

  • Memory, I/O, None
  • Cacheable/Non-cacheable
  • Write-back/Write-through
  • Read/write/read & write allocate, no allocate
  • Access fault for non-existent regions
Performance monitors Program code performance tuning

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 technology Performance throttling to digitally reduce power consumption
StackSafe™ hardware stack protection
  • Easy identification of stack size threshold during development
  • Hardware error detection of stack overflow and underflow at runtime
QuickNap™ technology Fast power-down/wake-up support for caches

* BSP v5.1.0, DMIPS/MHZ follow Dhrystone's no-inline ground rules, best performances 

Memory Subsystems

Key FeaturesBenefits

I-Cache & D-Cache

  • Size: 8KB to 64KB
  • Set associativity: Direct, 2-way or 4-way
  • Accelerating accesses to slow memories
  • Flexible cache configurations


  • Size: 4KB to 16M
  • SRAM or AXI interface support
  • Bus masters accesses by AXI slave port
  • For deterministic and efficient program execution
  • Flexible size selection to fit diversified needs
MemBoost – Data Cache Write-Around Smart cache line allocation policy, for better cache utilization and reduce number of memory accesses
MemBoost – Instruction and Data Pre-fetch Conditionally fill instruction and data caches in advance, for minimum memory access latency
MemBoost – Multiple Outstanding Mem. Req. Issue multiple transactions to data memory sub-system for higher bus utilization, also support out-of-order completion
MemBoost – Dedicated I & D Bus Interfaces Separate instruction and data buses, for instruction and data's own memory transactions
Soft-error protection: parity for I-Cache, and ECC for D-Cache, ILM and DLM Code and data integrity protection
Bus master port: AXI with 64-bit data, I/D joint or separate bus User-selectable bus interface for optimal efficiency
Bus save port: AXI with 64-bit data, for ILM/DLM accesses Efficient data transfer between CPU and SoC masters
Core/bus clock ratio of N:1 Simplified 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 specifications Supported by industry debug tool suppliers
JTAG Debug Port Industry-standard support
Embedded Debug Module with up to 8 triggers Flexible configurations to tradeoff between gate count and debugging capabilities
Exception redirection support Entering debugger upon selected exceptions without using breakpoints


Core, Process AX45, 28nm
Frequency (MHz) 1200
Dynamic power (uW/MHz) 33.6
Area (mm2) 0.232

Configured with 32KB instruction and data caches, MMU with 256-entry BTB, 16-entry PMP and 16-entry PMA, without DSP and FPU. Using 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

AndesCore™ AX45 Single-core Processor with AE350 AXI Platform

  • Pre-integrated AX45 single-core CPU subsystem, PLIC, Debug Module, and AXI Platform
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