Libre-Chip Awarded NLnet Grant to Prototype a CPU Isn't Vulnerable to Spectre

More information:

https://libre-chip.org/first_arch/index.html

https://web.archive.org/web/20201021124234/https://bugs.libr...

https://web.archive.org/web/20240610080828/https://groups.go...

https://danluu.com/branch-prediction/

> One idea I had for making a spectre-proof speculative execution engine is to build a theoretical model CPU such that it compares a branch oracle to the results of its branch prediction unit and takes the amount of time needed by the misprediction penalty when the branch predictor mispredicts, but doesn't actually execute any mispredicted instructions. This makes the model CPU unable to have spectre-style vulnerabilities since it doesn't do any actual speculative execution.

> Then, a physical CPU is built using the exact same design (where every instruction and every cache state change completes at the exact same clock cycle as the corresponding instruction in the theoretical model) but using speculative execution instead of the branch oracle. This gives a physical cpu that can be proven to not have any timing vulnerabilities that the model CPU doesn't have (ruling out spectre-style vulnerabilities) by proving that it follows the same steps as the model CPU.

Speculative execution > Variants,: https://en.wikipedia.org/wiki/Speculative_execution

Transient execution CPU vulnerability: https://en.wikipedia.org/wiki/Transient_execution_CPU_vulner...

Does RISC-V have speculative execution?

A RISC-V CPU out of graphene would be more efficient.

Interesting to see, hope they make progress on preventing the spectre attacks, since these are still relevant today. See this paper that was presented at the WHY2025 hacker camp: https://openreview.net/pdf?id=4tDNvQe2G0