This repository contains the source code of Lipsi and supports following paper:
Martin Schoeberl, Lipsi: Probably the Smallest Processor in the World, Architecture of Computing Systems -- ARCS 2018, Springer International Publishing, 2018, 18-30
While research on high-performance processors is important, it is also interesting to explore processor architectures at the other end of the spectrum: tiny processor cores for auxiliary tasks. While it is common to implement small circuits for auxiliary duties, such as a serial port, in dedicated hardware, usually as a state machine or a combination of communicating state machines, these functionalities may also be implemented by a small processor. In this paper we present Lipsi a very tiny processor to enable implementing classic finite state machine logic in software without overhead.
Lipsi is probably the smallest processor around. Possible evaluations of Lipsi: (1) an implementation of a serial port completely in software; (2) as Lipsi is so small we can explore a massive parallel multicore processor consisting of more than 100 Lipsi cores in a low-cost FPGA (with simple point-to-point connections between cores).
Lipsi is written in Chisel and contains: (1) the hardware description, (2) an assembler, (3) a software simulator, and (4) testers for individual testing and for co-simulation, all written in Chisel/Scala and combined in a single program. Chisel made it possible that the design of all of the above took less than 14 hours.
The Lipsi processor is beeing taped out with Tiny Tapeout. See a rendering of the actual GDS II file.
You need sbt and a JVM installed. Scala and Chisel are downloaded when
first used.
A plain
makeruns the default program as a test. The wave form can then be viewed with:
make wave
The default program can be overwritten with the variable APP:
make APP=asm/immop.asm
Lipsi executing the embedded hello world program, blinking and counting LEDs, can be generated as follows:
make hw APP=asm/blink.asm
The project contains a Quartus project in folder quartus.
All test cases are run with:
make test-all
The SW simulator of Lipsi is run with:
make sim
The co-simulation (for all tests) with the processor description in hardware and the SW simulator are run with:
make test-cosim
Folder asm contains various assembler program. E.g., echo.asm reads the keys from
the FPGA board, adds 1, and puts out the result on the LEDs (on the DE2-115).
Default IO devices are an 8-bit input port connected to the keys and 8-bit output
port connected to the LEDs
To build a 432 cores manycore version of Lipsi, change the value many to
val many = true in LipsiTop. The cores are then connected in a pipeline.
The echo.asm program can be used to execute 432 additions and show the result
on the LEDs.
As usual, have fun and feedback is appreciated,
Martin