Too bad Arm doesn't allow architectural licenses, because this is exactly the kind of thing Valve and the FEX developers would want to extend the ISA to support. I bet we see a RISC-V backend to FEX in the next 6 months, it probably already exists in a private repo.

FEX is the shootstring, extra special discount budget (not maligning) version of Rosetta. Apple should sell Rosetta to Valve.

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jsheard an hour ago | parent | next [-]

My understanding is that Rosetta sidesteps a bunch of tricky memory model issues by using non-standard hardware extensions only present in Apple Silicon, so even if Apple did share Rosetta, which they certainly won't, it wouldn't work properly on Valves hardware anyway.

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astrange 30 minutes ago | parent | next [-]

It's not only present in Apple Silicon, it's just not required by the ARM standard. Fujitsu also has an ARM64 CPU with TSO.

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fooblaster an hour ago | parent | prev [-]

yeah that is correct. The m series chips can turn on total store ordering memory model solely for Rosetta. There's also some hardware extensions to arm to support x86 condition codes in the hardware because it's way more instruction efficient that way.

	▲	sgerenser 24 minutes ago \| parent \| next [-]
		The latter is now an optional feature in the mainstream Arm ISA now (FEAT_FlagM and FEAT_FlagM2). Similarly the “alternate floating point mode” that Apple uses to match nuances of x86 FP semantics is a standard architectural feature as well. The TSO option though is Apples own thing.
	▲	astrange 26 minutes ago \| parent \| prev [-]
		If you mean FEAT_FlagM, that's standard in ARMv8.4. (There's also FlagM2 and AFP that are optional.) The JavaScript instruction is cooler though. https://developer.arm.com/documentation/dui0801/g/A64-Floati...

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geerlingguy an hour ago | parent | prev | next [-]

Box64 already runs on RISC-V. Just, the available processors are so slow it's hard to even play 5-10 year old games.

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nullbyte808 12 minutes ago | parent | prev | next [-]

better yet, Apple should make it open-source on github.

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JoshTriplett 2 hours ago | parent | prev [-]

> Too bad Arm doesn't allow architectural licenses

QEMU exists. I doubt they want the bad press of suing an Open Source project everyone is using.