[tybit]

It’s interesting that the author chose to use SHA256 hashing for the CPU intensive workload. Given they run on hardware acceleration using AES NI, I wonder how generally applicable it is. Still interesting either way though, especially since there were reports of earlier Graviton (pre v3) instances having mediocre AES NI performance.

[ComputerGuru]

Hardware-accelerated SHA support has a patchy history. I wrote an article some years ago about the prevalence of SHA instructions in x86 in x86_64 CPUs [0], like the current mess we see now with AVX-512, Intel invented something useful then declined to continue supporting it, while competitors that were late to the party became the real champions.

[0]: https://neosmart.net/blog/will-amds-ryzen-finally-bring-sha-...

[bobmcnamara]

Does AES NI imply SHA256 acceleration support?

[kbolino]

There are some crossed wires here.

AES-NI is x86-specific terminology. It was proposed in 2008. SHA acceleration came later, announced in 2013. The original version covers only SHA-1 and SHA-256 acceleration, but a later extension adds SHA-512 acceleration. At least for x86, AES-NI does not imply SHA support. For example, Westmere, Sandy Bridge, and Ivy Bridge chips from Intel have AES-NI but not SHA.

The equivalent in Arm land is called "Cryptographic Extensions" and was a non-mandatory part of ARMv8 announced in 2011. Both AES and SHA acceleration were announced at the same time. While part of the same extensions, there are separate feature flags for each of AES, SHA-1, and SHA-256.