E2 series


The SiFive E21 Standard Core is a high-performance, full-featured embedded processor designed to address advanced microcontroller applications such as Sensor Fusion, Smart IoT, Wearables, Connected Toys, and more. Separate Instruction and Data Buses, along with 2 banks of Tightly Integrated Memory (TIMs) make the E21 an ideal choice for applications with deterministic or demanding memory requirements.

Key Features
  • Machine and User Mode with 4 Region Physical Memory Protection
  • 3-stage pipeline with Simultaneous Instruction and Data Access
  • 2 Banks of Tightly Integrated Memory
  • System, Peripheral, and Front Ports
  • CLIC interrupt controller with 127 interrupts
  • Advanced debug with 4 hardware breakpoints/watchpoints
  • 2.27/1.62 DMIPS/MHz (Best Effort/Legal)
  • 3.31 CoreMark/MHz
  • Detailed Power, Performance, and Area (PPA) Information
E2 Series
Dhrystone Performance
1.62/2.27 DMIPS/MHza
1.25/1.89 DMIPS/MHz
CoreMark Performance with GCC
3.31 CoreMarks/MHzb
2.76 CoreMarks/MHz
Floating-Point Unit
Memory Map
Fixed ARMv7-M
Up to 1024 interrupts
240 interrupts
Interrupt latency to C handler
Memory Protection Regions
Up to 16 (optional)
0 or 8
Tightly Integrated Memory
2 Banks of TIM (optional)
Instruction Cache

a. E21 Standard Core Configuration, using GCC. The first score is using legal dhrystone compiler flags. The second score uses function inlining and link time optimizations.

b. E21 Standard Core Configuration, using GCC

c. CLIC Vectored Mode

Development Kit

Dev Kit Deliverables

  • RTL Evaluation
  • Test Bench RTL
  • Software Development Kit
  • FPGA Bitstream
  • Documentation
Series Overview

E2 Series

The E2 Series is highly optimized for area and power while still offering class-leading performance. Targeted for microcontroller and embedded devices, the E2 Core can be configured to be as small as 13.5k gates with an efficient 2‑stage pipeline or configured for higher performance with a 3‑stage pipeline, hardware floating-point, instruction cache, and more.

With SiFive Core Designer, the E2 Series can be fully customized to meet your specific requirements.

E2 Series

Key Features

  • Configurable core performance
  • Floating Point Unit, supporting Double, Single and Half precision
  • Custom memory map and ports
  • Optional Tightly Integrated Memory (TIM)
  • RV32E support with the smallest core configuration as small as 13.5k gates and is .005mm2 in 28nm
  • SiFive Insight Advanced Trace and Debug
  • Bit manipulation extension


  • MEMS Sensors
  • Power managment
  • Digital motor control
  • Low-power MCUs
  • Health wearable monitors
  • Environmental monitors

SiFive Essential
Standard Cores

Standard Cores
Arm Comparison
E2 Series
M0, M0+, M3, M4, M23, M33
E6 Series
R4, R5
E7 Series
M7, R7, R8
S2 Series
S6 Series
R4, R5
S7 Series
M7, R7, R8
U6 Series
A5, A7, A35
U7 Series
A53, A55
Core Evaluation

From idea to reality.

Ready to see your code in action? The E21 Development Kit enables free evaluation of SiFive RISC-V Core IP.


Evaluation RTL

  • Full-Functional, synthesizable Verilog RTL
  • Run it in your own simulator
  • Simple, no-cost evaluation license
Start E21 Free Trial

FPGA Bitstream

  • Fully-functional SiFive RISC-V Core Complex with system peripherals
  • High Performance - 32.5 MHz emulation
  • Upload your own programs using the Freedom E SDK

Compatible with the Arty A7-100T and Xilinx VCU118 FPGA Development Boards: