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A comment on Exercises in Emulation: Xbox 360’s FMA Instruction.

Re:Exercises in Emulation: Xbox 360’s FMA Instruction by anisppp on Thursday March 21, 2019 @08:45AM (#19451640)
Personally found this article overly dramatic and a bit dumb. All this wall of text just to point out that FMA needs to be emulated... ok.. but it’s a solved problem. This is also not a new problem.. fmaf is defined in C99 standard so There are multiple open source library implementations of FMA using round to odd for years.

You can just read that code and see how it’s done. Despite the ridiculous ending there was no mystery to begin with.

https://www.lri.fr/~melquion/doc/08-tc.pdf

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Re:Exercises in Emulation: Xbox 360’s FMA Instruction by eindiran on Thursday March 21, 2019 @02:26PM (#19455665)
That is weird. The paper was published in 2009 by Microsoft Research, and the Xbox One entered development in early 2011 according to Wikipedia (https://en.wikipedia.org/wiki/Xbox_One). So when the author started working on the problem for Microsoft, Microsoft already knew how to solve the problem.
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Re:Exercises in Emulation: Xbox 360’s FMA Instruction by brucedawson on Thursday March 21, 2019 @04:20PM (#19456834)
Author here: I don't remember exactly when I did my investigation but I left the Xbox team in early 2009, so it would have been some time before that.

The 2011 date from Wikipedia is for when hardware development began. Investigations into what hardware would be used would obviously predate that so there's no contradiction.

Anyway, I'll have to digest that FMA emulation article and see what sort of performance their algorithm achieves. A branchless and vector-math compatible implementation would be important for performance.

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Re:Exercises in Emulation: Xbox 360’s FMA Instruction by eindiran on Thursday March 21, 2019 @06:56PM (#19458186)
Thank you for response/clarifying the timeline. I didn't realize that development on non-hardware parts of the system would happen so much earlier, but it makes sense that you'd want to know if changing archs made your catalog unplayable!
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Re:Exercises in Emulation: Xbox 360’s FMA Instruction by dogen on Thursday March 21, 2019 @02:57PM (#19456047)
it's possible he left before that. they were working on xbox 360 bc for a long time.
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