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If you take a Zen 3 running at optimal clocks for efficiency (such as the 5800U) the difference between its computing performance per watt is competitive with t
by Salgat 4y ago
If you take a Zen 3 running at optimal clocks for efficiency (such as the 5800U) the difference between its computing performance per watt is competitive with the M1 if you account for the difference in node size (which TSMC claims gives 30% less power consumption at the same performance). As the article points out, the real efficiency gains will be domain specific changes such as shifting to 8 bit for more calculations.
- jorvi 4y agoHow would x86-64 be as efficient with the same transistor & power budget when they have to run an extra decoder and ring within that budget? Seems physically impossible.
- Salgat 4y agoMy guess is it's related to the higher transistor count. The M1 for example has 16B transistors compared to the 5800U with 10.7B.
- Panzer04 4y agoAs I understand it, the actual processing part of most chips nowadays is fairly bespoke, with a decoder sitting on top. I doubt decode can make up that large a portion of a chips power consumption (probably negligible next to the rest of the chip?), so other improvements can make up for the difference.
- ejiblabahaba 4y agoI found this to be a pretty expansive answer to this question: https://chipsandcheese.com/2021/07/13/arm-or-x86-isa-doesnt-matter/ https://chipsandcheese.com/2021/07/13/arm-or-x86-isa-doesnt-...
- jorvi 4y agoThank you for the detailed article!
- jabl 4y agoAll else being equal, they can't. But the difference isn't as big as some people like to think. For a current high end core, probably low single digit %. And x86-64 has had a lot more effort going into software optimization.
- monocasa 4y agoBecause the more complex decoder is traded in this case for a denser instruction set, which means they can trade it for less instruction cache (which is more power hungry).
- chasil 4y agoHow can AArch64 be as efficient when it implements all of the old 32-bit extensions? Some don't, but a phone does.
- appointment 4y agoThe latest ARM Cortex CPUs (models X2, A715 and A510) drop 32-bit support. Qualcomm actually includes two older Cortex-A710 cores in the Snapdragon 8 gen 2 for 32-bit support. Don't know much about Apple Silicon but didn't they drop 32-bit a couple of years back? Google has purged 32-bit apps from the official Android app store, but as I understand it the Chinese OEMs that ship un-Googled AOSP ROMs with their own app stores haven't been as aggressive about moving to 64-bit.
- deleted 4y ago[deleted]
- shaunsingh0207 4y agoApple also entirely drops 32-bit from their arm systems
- snovv_crash 4y agoThe decoder has negligible power consumption and die area on a modern CPU.
- zozbot234 4y agoNot if you have a complex ISA like x86 and want a very wide decode.
- peoplefromibiza 4y agoyes if you want to keep the transistor count low M1 has 16 billion of them AMD is below 10 billion
- peoplefromibiza 4y ago> when they have to run an extra decoder it's not that expensive it's a tradeoff, you lose something there, you gain somewhere else. x86 has a more complex decoder exactly because it was less powerful and had to save on computing power and energy consumption, not being a mainframe.
- senttoschool 4y agoIt really isn't competitive. First of all, when you downclock anything, you're going to gain efficiency. If Apple downclocks M1, it can get even more efficient. Second, most of these tests use Cinebench, which is highly optimized for x86, not ARM instructions. Geekbench should be used instead. Third, the M1 is a SoC. Everything is on it. Everything is efficiently connected directly inside the chip.
- Salgat 4y agoBoth the M1 and 5800U run around 15W and are already clocked for efficiency. The M1 Max is their higher clocked less efficient offering.
- senttoschool 4y agoThis is false. The 5800U will boost well beyond 15w. Ignore their TDP marketing ratings.