S2 Series
S21
The SiFive S21 Standard Core is a full-featured 64-bit embedded processor based on the S2 Series. The S21 has separate Instruction and Data Buses, along with 2 banks of Tightly Integrated Memory (TIMs). The S21 is an ideal choice for area constrained applications demanding a 64-bit processor.

S21 Key Features
- RISC-V ISA - RV64IMABC
- 64-bit AXI Ports
- 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
- CLIC interrupt controller with 127 interrupts
- Advanced debug with 4 hardware breakpoints/watchpoints
- 2.54/1.72 DMIPS/MHz (Best Effort/Legal)
- 3.36 Coremarks/MHz
- Detailed Power, Performance, and Area (PPA) Information
a. S21 Standard Core Configuration, using GCC
b. CLIC Vectored Mode
S21 Development Kit
Dev Kit Deliverables
- RTL Evaluation
- Test Bench RTL
- Software Development Kit
- FPGA Bitstream
- Documentation
Series Overview
S2 Series
The S2 Series is a 64-bit microcontroller highly-optimized for area, efficient performance, and simplified integration into 64-bit SoCs. The S2 core has the same efficient 2‑stage or 3-stage pipeline as the E2 Series as well as a Core Local Interrupt Controller (CLIC) enabling extremely fast interrupt response. The S2 Series can be fully customized to meet your specific requirements.
S2 Series Highlights
Key Features
- 64-bit CPU
- Greater than 32-bit physical address
- Optional Tightly Integrated Memory (TIM)
- Configurability
- Physical addressing up to 47-bits
- Support for SiFive Insight Advanced Trace and Debug
- Floating Point Unit, supporting Double, Single and Half precision
- Bit manipulation extension
Applications
- 64-bit Embedded Controller
- Consumer
- Industrial Automation
- Management Core
Core Evaluation
From idea to reality.
Ready to see your code in action? The S21 Development Kit enables free evaluation of SiFive RISC-V Core IP.
Key
Deliverables
Evaluation RTL
- Full-Functional, synthesizable Verilog RTL
- Run it in your own simulator
- Simple, no-cost evaluation license
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: