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Comment by ldng | Hacker News Reader

I'm unsure of the security of simultaneous multithreading on modern Apple CPUs

I’m unsure of the existence of simultaneous multithreading on Apple CPUs.

I'm unsure of the security of anything on modern Apple operating systems or hardware, since I can't review the source code or hardware schematics.

Can you send me the Intel/AMD/Qualcomm/Samsung sources and schematics?

Intel at very least do publish a pretty hefty optimization manual.

We do have a bunch of leaked intel firmware, or so I'm told...

I haven't followed it or tried it, but supposedly you can boot up a pure open source Darwin system. Certainly it has been very useful for me as a cross-platform developer to be able to browse its source and understand quirks of system calls etc. Are you saying that key parts you'd like to review are closed source? Hmm, the new file system is closed source, which is a clue, but I don't know to what extent Darwin is "different" from what macOS is really running...

I haven’t kept up with this too much lately, but to my knowledge there is very little documentation or working code to set up a Darwin environment from scratch with FOSS, and there aren’t any modern Darwin “distributions” because of this difficulty and lack of documentation and code.

I wish this weren’t the case, but whatever PureDarwin has right now is probably about the closest you can get to a Darwin environment that boots without nonfree code.

Apple cpus specifically, or arm64 in general? The same class of bug (i.e., speculative execution) or something else altogether?

I’ve found myself with more and more arm hardware these days, and I’d assumed (probably incorrectly) that it wasn’t as prone to these kinds of issues.

> simultaneous multithreading on modern Apple CPUs reply

Where did you find such a thing?

I’m not well versed in architecture intricacies of arm64, simultaneous multithreading doesn’t exist on those platforms?

Architecture: ARMv8 or ARMv7.

Microarchitecture: Neoverse N2, NeoverseE1, Apple Firestorm (all the same ARMv8 architecture, but all different microarchitectures)

Of these: Neoverse E1 has SMT. Apple Firestorm does not.

Cavium ThunderX2 (RIP) had 4-way SMT

Can you share some of your research about it?

Reply on news.ycombinator.com