07-02-2020, 07:53 AM
https://www.extremetech.com/computing/31...nce-vs-x86
Quote:Ever since Apple announced the A12Z and its shift away from x86, there’ve been questions about exactly how these ARM chips will perform and what we can expect from them. The first benchmark results are starting to appear from Apple dev kits, and as long as you take them with a mountain of salt, they’re pretty interesting.
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One thing to keep in mind is that emulation performance can vary drastically depending on the application. Some programs might run with relatively small penalties, while others crater and die. Rosetta 2 is specifically designed to avoid those outcomes, but historically, there’s a nasty corner case or two lurking somewhere in any emulator. Some applications are harder to emulate than others. But the upshot of this effect is that we don’t really know if that 1.44x lead the 13-inch MacBook has is the product of emulator handicapping or if it’s a pretty good look at the CPU’s performance. Data from the iPad Pro suggests it might be the former.
If we assume that the A12X in the iPad Pro is a pretty good stand-in for the A12Z, we can check ARM-native Geekbench performance, albeit in iOS, not macOS. Here, we’re looking at 1120 single-core, 4650 multi-core, with a scaling factor of 4.16x. The MacBook Pro 13-inch is only about 8 percent faster than the iPad Pro in single-thread, and 10 percent slower in multi-thread.
Frankly, that should send a frisson of fear through Intel and AMD. The implication of these results is that the gap between the 13-inch Mac and the A12Z is largely the result of emulation. That’s not a guarantee, because OS differences matter in situations like this, but it certainly looks as though most of the penalty the A12Z is carrying is related to emulating x86 code.
Apple’s year-on-year record of delivering new performance improvements is considerably better than Intel’s right now. AMD can make a much stronger argument for its own recent improvement, thanks to Ryzen, but the enormous 1.52x IPC improvement from Excavator to Ryzen tilts the comparison a bit. To put it bluntly, AMD’s improvements the last three years would be a little less impressive if Bulldozer hadn’t been such an awful chip to start with.
We’re in a weird situation at the moment. Intel has always been Apple’s chief supplier, but AMD is selling more performant mobile CPUs today, making them the more obvious point of comparison. The 4900HS appears to score a 1116 single-core and a 7013 multi-threaded score. x86 MT is, at least, in no immediate danger, in absolute terms. Keep in mind that the 4900HS also draws far more power than either the Intel or Apple chips.
What we see here isn’t proof that Apple will launch a MacBook ARM chip that rivals the best Intel and AMD can offer. But it certainly puts a floor under expected performance, barring unusual emulator quirks that Apple will spend the next few months quashing. The x86 companies may want to ask their mobile CPU designers to put an extra pot of coffee on.