The study items are listed on the Open Source CPUs post, especially the category description.

OpenRisc

The goal of the project fits my view of open source hardware, nice 😉
They claim a stable status and both fpga and asic proven design, well after reading the OpenRisc 1000 is a family specification, so this really applies to the OR1200 which is the only actual implementation existing today. It’s a 32bit RISC CPU with Harvard architecture, caches and MMU.
So it fits in the portable CPU category.

OpenSparc

It really look like sun needed some publicity to me, anyway here it is, a strong high end CPU (8 cores 64bit Risc…) it’s released under GPL v2. I don’t know if oracle buying sun interfered here, but some link on the site were broken, and the data did not seam to be that recent… But if it’s stable they don’t need more releases. Finally it’s really too high end for any geeky project, but there is a more suitable fork: look at S1 Core.

Simply RISC S1 Core

This is a reduced version of OpenSparc T1 with a single core, so it’s still a powerful 64bit Risc, but I think it’s more accessible so it fits the portable CPU category.

Note: From the S1 Core project page on OpenCores the same maintainers started a new and similar project OpenSPARC-based SoC

A summary table including those CPU is available, currently only in OpenOffice Format: Open Cpu Study Summary.

I recently blogged about Open Source Hardware, lets take a look a bit more at the FPGA/ASIC kind of projects.

Any project big enough will require a CPU to control the rest of the hardware and maybe just run some user software. So we need an open source CPU ! That is to say, the code of a processor in a common HDL language (VHDL, verilog) with an open source licence.

A quick search on the internet and we have plenty of soft-processor, some open source, some not:

• Soft microprocessor on wikipedia
• Processor projects on OpenCores

So how do we compare all that ?

There is an interesting article on the subject on 1-code technologies: Soft CPU Cores for FPGA. It compares the cpu in terms of features and size (in FPGA cells).
(As too often on the internet it’s lacking a publication date so it’s hard to know how recent the information is.)

So I’m planning to review several CPU and publish my results.

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