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Why is Rosetta 2 fast?

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Re: Why is Rosetta 2 fast?

#191

Post by Klonoar »

cwzwarich wrote: post #111
darzu wrote: post #76

Does anyone know the names of the key people behind Rosetta 2? In my experience, exceptionally well executed tech like this tends to have 1-2 very talented people leading. I'd like to follow their blog or Twitter.

I am the creator / main author of Rosetta 2. I don't have a blog or a Twitter (beyond lurking).

Huh, this is timely. Incredibly random but: do you know if there was anything that changed as of Ventura to where trying to mmap below the 2/4GB boundary would no longer work in Rosetta 2? I've an app where it's worked right up to Monterey yet inexplicably just bombs in Ventura.

Re: Why is Rosetta 2 fast?

#192

Post by GeekyBear »

kijiki wrote: post #146
iainmerrick wrote: post #23

This is a great writeup. What a clever design! I remember Apple had a totally different but equally clever solution back in the days of the 68K-to-PowerPC migration. The 68K had 16-bit instruction words, usually with some 16-bit arguments. The emulator’s core loop would read the next instruction and branch directly into a big block of 64K x 8 bytes of PPC code. So each 68K instruction got 2 dedicated PPC instructions…

> Anyone know how they implemented PPC-to-x86 translation? They licensed Transitive's retargettable binary translator, and renamed it Rosetta; very Apple. It was originally a startup, but had been bought by IBM by the time Apple was interested.

> It was originally a startup, but had been bought by IBM by the time Apple was interested.

Rosetta shipped in 2005.

IBM bought Transitive in 2008.

The last version of OS X that supported Rosetta shipped in 2009.

I always wondered if the issue was that IBM tried to alter the terms of deal too much for Steve's taste.

Re: Why is Rosetta 2 fast?

#193

Post by duskwuff »

scarface74 wrote: post #105
Asmod4n wrote: post #41

Earlier quoted context omitted.

I don't know how they did it, but they did it very very slowly. Anything "interactive" was unuseable.

Interactive 68K programs were usually fast. The 68K programs would still call native PPC QuickDraw code. It was processor intensive code that was slow. Especially with the first generation 68K emulator. Connectix SpeedDoubler was definitely faster.

Most of the Toolbox was still running emulated 68k code in early Power Mac systems. A few bits of performance-critical code (like QuickDraw, iirc) were translated, but most things weren't.

Re: Why is Rosetta 2 fast?

#194

Post by classichasclass »

dev_tty01 wrote: post #127
scarface74 wrote: post #110

Earlier quoted context omitted.

> Their first 68k -> PPC emulator (Davidian's) was so good that for some things the PPC Mac was the fastest 68k mac you could buy. This is not true. A 6100/60 running 68K code was about the speed of my unaccelerated Mac LCII 68030/16. Even when using SpeedDoubler, you only got speeds up to my LCII with a 68030/40Mhz accelerator. Even the highest end 8100/80 was slower than a high end 68k Quadra. The only time 68K cod…

>The only time 68K code ran faster is when it made heavy use of the Mac APIS that were native. Yes, and that just confirms the original point. Mac apps often spend a lot of time in the OS apis and therefore the 68K code (the app) often ran faster on PPC than it did on 68K because apps often spend much of their time in OS apis. The earlier post said "so good that for some things the PPC Mac was the fastest 68k mac." T…

Part of that was the greater clock speeds on the 601 and 603, though. Those started at 60MHz. Clock for clock 68K apps were generally poorer on PowerPC until PPC clock speeds made them competitive, and then the dynamic recompiling emulator knocked it out of the park.

Similarly, Rosetta was clock-for-clock worse than Power Macs at running Power Mac applications. The last generation G5s would routinely surpass Mac Pros of similar or even slightly greater clocks. On native apps, though, it was no contest, and by the next generation the sheer processor oomph put the problem completely away.

Rosetta 2 is notable in that it is so far Apple's only processor transition where the new architecture was unambiguously faster than the old one on the old one's own turf.

Re: Why is Rosetta 2 fast?

#195

Post by dahfizz »

bluGill wrote: post #179
mikepurvis wrote: post #104

Earlier quoted context omitted.

I think I landed in a place where it's basically "the compiler has insufficient information to achieve ideal optimization because some things can only be known at runtime." Which is not exclusively an argument for runtime JIT— it can also be an argument for instrumenting your runtime environment, and feeding that profiling data back to the compiler to help it make smarter decisions the next time. But that's definitel…

The problem with JIT is not all information known at runtime is the correct information to optimize one. In finance the performance critical code path is often the one run least often. That is you have a if(unlikely_condition) {run_time_sensitive_trade();}. In this case you need to tell the compiler to ensure the CPU will have a pipeline stall because of a branch misprediction most of the time to ensure the time that…

The other issue with JIT is that it is unreliable. It optimizes code by making assumptions. If one of the assumptions is wrong, you pay a large latency penalty. In my field of finance, having reliably low latency is important. Being 15% faster on average, but every once in a while you will be really slow, is not something customers will go for.

Re: Why is Rosetta 2 fast?

#196

Post by runjake »

kijiki wrote: post #146
iainmerrick wrote: post #23

This is a great writeup. What a clever design! I remember Apple had a totally different but equally clever solution back in the days of the 68K-to-PowerPC migration. The 68K had 16-bit instruction words, usually with some 16-bit arguments. The emulator’s core loop would read the next instruction and branch directly into a big block of 64K x 8 bytes of PPC code. So each 68K instruction got 2 dedicated PPC instructions…

> Anyone know how they implemented PPC-to-x86 translation? They licensed Transitive's retargettable binary translator, and renamed it Rosetta; very Apple. It was originally a startup, but had been bought by IBM by the time Apple was interested.

Link: https://en.wikipedia.org/wiki/QuickTransit

Re: Why is Rosetta 2 fast?

#197

Post by sergimas15 »

hinkley wrote: post #15

I remember years ago when Java adjacent research was all the rage, HP had a problem that was “Rosetta lite” if you will. They had a need to run old binaries on new hardware that wasn’t exactly backward compatible. They made a transpiler that worked on binaries. It might have even been a JIT but that part of the memory is fuzzy. What made it interesting here was that as a sanity check they made an A->A mode where they…

No post body was provided.

Re: Why is Rosetta 2 fast?

#198

Post by runjake »

lostgame wrote: post #136
iainmerrick wrote: post #23

This is a great writeup. What a clever design! I remember Apple had a totally different but equally clever solution back in the days of the 68K-to-PowerPC migration. The 68K had 16-bit instruction words, usually with some 16-bit arguments. The emulator’s core loop would read the next instruction and branch directly into a big block of 64K x 8 bytes of PPC code. So each 68K instruction got 2 dedicated PPC instructions…

From what I understand; they purchased a piece of software that already existed to translate PPC to x86 in some form or another and iterated on it. I believe the software may have already even been called ‘Rosetta’. My memory is very hazy; though. While I experienced this transition firsthand and was an early Intel adopter, that’s about all I can remember about Rosetta or where it came from. I remember before Adobe h…

Link: https://en.wikipedia.org/wiki/QuickTransit

Re: Why is Rosetta 2 fast?

#199

Post by keepquestioning »

cwzwarich wrote: post #111
darzu wrote: post #76

Does anyone know the names of the key people behind Rosetta 2? In my experience, exceptionally well executed tech like this tends to have 1-2 very talented people leading. I'd like to follow their blog or Twitter.

I am the creator / main author of Rosetta 2. I don't have a blog or a Twitter (beyond lurking).

Isn't Rosetta 2 "done"? What are you working on now?

Re: Why is Rosetta 2 fast?

#200

Post by hawflakes »

hinkley wrote: post #15

I remember years ago when Java adjacent research was all the rage, HP had a problem that was “Rosetta lite” if you will. They had a need to run old binaries on new hardware that wasn’t exactly backward compatible. They made a transpiler that worked on binaries. It might have even been a JIT but that part of the memory is fuzzy. What made it interesting here was that as a sanity check they made an A->A mode where they…

People have mentioned the Dynamo project from HP. But I think you're actually thinking of the Aries project (I worked in a directly adjacent project) that allowed you to run PA-RISC binaries on IA-64.

https://nixdoc.net/man-pages/HP-UX/man5/Aries.5.html

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