Microwatt is an

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

soft processor core originally written in

VHDL VHDL (Very High Speed Integrated Circuit Program, VHSIC Hardware Description Language) is a hardware description language that can model the behavior and structure of Digital electronics, digital systems at multiple levels of abstraction, ran ...

by Anton Blanchard at

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

, announced at the OpenPOWER Summit NA 2019OpenPOWER Summit NA 2019: Day 2 Keynote Demonstration: Anton Blanchard, IBM & Joe DeLaere, Xilinx
/ref> and published on

GitHub GitHub () is a Proprietary software, proprietary developer platform that allows developers to create, store, manage, and share their code. It uses Git to provide distributed version control and GitHub itself provides access control, bug trackin ...

in August 2019. It adheres to the Power ISA 3.0

instruction set In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, s ...

and can be run on FPGA boards, booting

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

MicroPython MicroPython is a software implementation of a programming language largely compatible with Python 3, written in C, that is optimized to run on a microcontroller. MicroPython consists of a Python compiler to bytecode and a runtime interpreter o ...

and

Zephyr In European tradition, a zephyr is a light wind or a west wind, named after Zephyrus, the Greek god or personification of the west wind. Zephyr may also refer to: Arts and media Fictional characters * Zephyr (comics), in the Marvel Comics univers ...

."POWER OpenISA and Microwatt introduction" - Anton Blanchard (LCA 2020)
/ref>"Microwatt Microarchitecture" - Paul Mackerras (LCA 2020)
/ref>

Design

Microwatt is a tiny

64-bit In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide. Also, 64-bit central processing units (CPU) and arithmetic logic units (ALU) are those that are based on processor registers, a ...

bi-endian '' Jonathan_Swift.html" ;"title="Gulliver's Travels'' by Jonathan Swift">Gulliver's Travels'' by Jonathan Swift, the novel from which the term was coined In computing, endianness is the order in which bytes within a word (data type), word of d ...

scalar Scalar may refer to: *Scalar (mathematics), an element of a field, which is used to define a vector space, usually the field of real numbers *Scalar (physics), a physical quantity that can be described by a single element of a number field such a ...

integer An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...

processor core, implementing a subset of the Power ISA 3.0 instruction set. It has 32× 64-bit

general purpose registers A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-onl ...

and 32x 64-bit

floating-point registers In computing, floating-point arithmetic (FP) is arithmetic on subsets of real numbers formed by a ''significand'' (a signed sequence of a fixed number of digits in some base) multiplied by an integer power of that base. Numbers of this form ...

. It uses Wishbone for the memory interface. The initial development was done in a couple of months, included the entire integer processing functionality of the instruction set; the bare minimum to make it compliant, with no

memory management unit A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit that examines all references to computer memory, memory, and translates the memory addresses being referenced, known as virtual mem ...

(MMU) and no

floating-point unit A floating-point unit (FPU), numeric processing unit (NPU), colloquially math coprocessor, is a part of a computer system specially designed to carry out operations on floating-point numbers. Typical operations are addition, subtraction, multip ...

. Later additions to the implementation includes

JTAG JTAG (named after the Joint Test Action Group which codified it) is an industry standard for verifying designs of and testing printed circuit boards after manufacture. JTAG implements standards for on-chip instrumentation in electronic design ...

debugger interface, divider instructions, 16 KB instruction and 32 KB data caches, a non-hypervisor-capable MMU, pipelining and

floating-point In computing, floating-point arithmetic (FP) is arithmetic on subsets of real numbers formed by a ''significand'' (a Sign (mathematics), signed sequence of a fixed number of digits in some Radix, base) multiplied by an integer power of that ba ...

support. It's designed using VHDL 2008 and the GHDL simulation environment.

Chiselwatt

A sibling project called Chiselwatt is another open processor core implementing the Power ISA 3.0 instruction set, written in the Scala-based Chisel instead of VHDL.

Implementations

* Microwatt itself *

Libre-SOC Libre-SOC was a project by Luke Leighton and other contributors to build a libre soft processor core, announced at the OpenPOWER Summit NA 2020. It adhered to the Power ISA 3.0 instruction set and could be run on field-programmable gate array ...

– A

libre Libre may refer to: Computing * Libre software, free software * Libre Computer Project, developer of open-hardware single-board computers Medicine *FreeStyle Libre, a glucose monitoring device Music * ''Libre'' (Alejandra Guzmán album) * ''Li ...

system on a chip A system on a chip (SoC) is an integrated circuit that combines most or all key components of a computer or Electronics, electronic system onto a single microchip. Typically, an SoC includes a central processing unit (CPU) with computer memory, ...

under development that uses Microwatt as a

reference design A reference design is a technical design of a system that is intended for others to copy. It contains the essential elements of the system; however, third parties may enhance or modify the design as required. When discussing computer designs, th ...

. * Kestrel – A soft BMC in Raptor Engineering POWER9 based workstations.

History

It is the first processor written from scratch using the open Power ISA 3.0, and is released by the OpenPOWER Foundation as a reference design. The project started as a demo, proof of concept and a reference implementation for the release of the opensource initiative regarding Power ISA 3.0. The goal for Blanchard was to see if he could make it, and as a software developer, taking on a very low level hardware project was a challenge. Microwatt is set to be fabricated in

130 nm The 130 nanometer (130 nm) process is a level of semiconductor process technology that was reached in the 2000–2001 timeframe by such leading semiconductor companies as Intel, Texas Instruments, IBM, and TSMC. The origin of the 130 nm v ...

by Efabless "Open MPW Shuttle Program" in 2021. As of February 2024, there has been no update on the progress of fabrication on Efabless's Microwatt project page.

References

External links