OpenPOWER Microwatt
| Company type | Open source project |
|---|---|
| Industry | Semiconductor / Microprocessor design |
| Founded | 2019 |
| Founder | Anton Blanchard |
| Headquarters | International |
| Products | Soft processor core implementing Power ISA 3.0 |
| Website | github |
Microwatt is an open source soft processor core initially created in VHDL by Anton Blanchard at IBM. It was introduced during the OpenPOWER Summit NA 2019 and made available on GitHub in August 2019. Microwatt supports the Power ISA version 3.0 instruction set architecture and operates on FPGA platforms, compatible with operating systems such as Linux, MicroPython, and Zephyr.
Design
Microwatt is a streamlined, 64-bit bi-endian scalar integer core that implements a portion of the Power ISA 3.0 instruction set. It includes 32 general purpose registers and 32 floating-point registers, each 64 bits wide, and utilizes the Wishbone bus interface for memory communication.
The initial design phase, lasting several months, focused on delivering full integer processing capabilities to meet compliance standards, initially excluding an memory management unit (MMU) and a floating-point unit. Later revisions incorporated features such as a JTAG debugger, division instructions, instruction and data caches sized at 16 KB and 32 KB respectively, a non-hypervisor MMU, pipelining enhancements, and floating-point processing support.
The entire core is described using VHDL 2008 and tested through simulations with the GHDL toolchain.
Chiselwatt
Chiselwatt is another open-source processor core implementing Power ISA 3.0, but developed in Chisel—a hardware construction language based on Scala—rather than VHDL.
Implementations
- The Microwatt core itself
- Libre-SOC – An open-source system-on-chip project under development that uses Microwatt as a foundational reference
- Kestrel – A soft Baseboard Management Controller (BMC) integrated within Raptor Engineering POWER9 workstation systems
History
Microwatt represents the first processor designed entirely from the ground up using the open Power ISA 3.0 specification and released by the OpenPOWER Foundation as a reference implementation. Originating as a proof-of-concept project to showcase the open-source Power ISA initiative, it was spearheaded by Anton Blanchard, who moved from software engineering into hardware design at a low level.
Plans were made to manufacture Microwatt using a 130 nm process technology through Efabless's "Open MPW Shuttle Program" scheduled for 2021. However, as of February 2024, no fabrication updates have been posted on Efabless’s official project page.