8 ms·

So is ARM the future at this point? After seeing how well Apple's M1 performed against a traditional AMD/Intel CPU, it has me wondering. I used to think that AR

by lprd 5y ago

So is ARM the future at this point? After seeing how well Apple's M1 performed against a traditional AMD/Intel CPU, it has me wondering. I used to think that ARM was really only suited for smaller devices.

fulafel 5y ago
The instruction set doesn't make a significant difference technically, the main things about them are monopolies (patents) tied to ISAs, and sw compatibility.
- rvanlaar 5y ago
  I'm interested in your thoughts on why this doesn't make a significant difference. From what I've read, the M1 has a lot of tricks up its sleeve that are next to impossible on X86. For example ARM instructions can be decoded in parallel.
  - fulafel 5y ago
    Instruction decoding is more power efficient on arm, but x86 has solved it as a perf bottleneck, with the trace/uop caches and by doing some speculative work in the decoders. (Parallel decoding is also old hat and not a M1 or ARM land invention, it's trivial with RISC style insn format.). What other tricks do you have in mind? More broadly, as to why the ISA doesn't make a big difference: The major differences are at the microarchitecture level since OoO processors have such flexible dataflow machinery in them that you can kind of view the frontend as compiler technology. x86 and ARM are decades-old ISAs that have seen a many many rounds of iteration in form of added instructions and even backwards incompatible reboots at the 64-bit transition points so most hinderances have been fixed. In the olden days ISAs were important because processors were orders of magniture simpler, and instructions were processed as-is very statically (to the point that microarchitectural artifacts like branch delay slots were enshrined in some ISAs). This meant that eg the complexity of individual instructions could a bottleneck to how fast a chip could be clocked. Or in CISC land your ISA might have been so complex that the CPU was a microcoded implementation of the ISA and didn't have any hardwired fast instructions...
mhh__ 5y ago
The next decade is ARM's for the taking, but if Intel and AMD can make good cores then it's not anywhere close to slam dunk. One of the reasons why M1 is good is pure and simple that it has a pretty enormous transistor budget, not solely because it's ARM.
- tambourine_man 5y ago
  >…is pure and simple that it has a pretty enormous transistor budget There's a lot of brute force, yes, but it's not the only reason. There are lots of smart design decisions as well.
  - mhh__ 5y ago
    "One of the reasons" I did say.
    - tambourine_man 5y ago
      True, I misread it.
  - amelius 5y ago
    Yes, but those decisions optimize for the single user laptop case, not for e.g. servers.
- api 5y ago
  Being ARM has something to do with it. The x86 instruction decoder may be only about ~5% of the die, but it's 5% of the die that has to run all the time. Think about how warm your CPU gets when you run e.g. heavy FPU loads and then imagine that's happening all the time. You can see the power difference right there. It's also very hard to achieve more than 4X parallelism (though I think Ice Lake got 6X at some additional cost) in decode, making instruction level parallelism harder. X86's hack to get around this is SMT/hyperthreading to keep the core fed with 2X instruction streams, but that adds a lot more complexity and is a security minefield. Last but not least: ARM's looser default memory model allows for more read/write reordering and a simpler cache. ARM has a distinct simplicity and low-overhead advantage over X86/X64.
bitwize 5y ago
> So is ARM the future at this point? The near future. A few years out, RISC-V is gonna change everything.
kllrnohj 5y ago
It will come down entirely to who can sustain a good CPU core. Currently Apple is the only company making performance-competitive ARM cores that can make a reasonable justification for an architecture switch. Otherwise AMD's CPUs are still ahead of everyone else, including all other ARM CPU cores not made by Apple. And even Intel is still faster in places where performance matters more than power efficiency (eg, desktop & PC gaming)
- floatboth 5y ago
  Arm's Neoverse cores are doing pretty well in the datacenter space — on AWS, the Graviton2 instances are currently the best ones for lots of use cases. It's clear that core designs by Arm are really good. The problem currently is the lag between the design being done and various vendors' chips incorporating it. upd: oh also in the HPC world, Fujitsu with the A64FX seems to be like the best thing ever now
  - rubatuga 5y ago
    Fujitsu flying under the radar while having the fastest cpu ever made haha
  - kllrnohj 5y ago
    Graviton2 is competitive sometimes with Epyc, but also falls far behind in some tests (eg, Java performance is a bloodbath). Overall across majority tests, Neoverse consistently comes up short of Milan even when Neoverse is given a core-count advantage. And critically the per-core performance of Graviton2 / Neoverse is worse, and per-core performance is what matters to consumer space. But it can't just be competitive it needs to be significantly better in order for the consumer space to care. Nobody is going to run Windows on ARM just to get equivalent performance to Windows on X86, especially not when that means most apps will be worse. That's what's really impressive about the M1, and so far is very unique to Apple's ARM cpus. > oh also in the HPC world, Fujitsu with the A64FX seems to be like the best thing ever now A64FX doesn't appear to be a particularly good CPU core, rather it's a SIMD powerhouse. It's the AVX-512 problem - when you can use it, it can be great. But you mostly can't, so it's mostly dead weight. Obviously in HPC space this is different scenario entirely, but that's not going to translate to consumer space at all (and it's not an ARM advantage, either - 512bit SIMD hit consumer space via x86 first with Intel's Rocket Lake).
CalChris 5y ago
Apple isn't entering the cloud market. Moreover the M1 isn't a cloud cpu. The M1 SOC emphasizes low latency and performance per watt over throughput.
- enos_feedler 5y ago
  AWS has Mac mini, and is expected to add M1 mini into the mix [1]. I expect Apple to take lots of silicon design into data centers and edge computing. Over time I can see a lot of mobile apps running backend through Apple silicon with a full Apple cloud software stack to provide data management around security and privacy. 1. https://9to5mac.com/2021/02/02/m1-mac-mini-in-the-cloud/ https://9to5mac.com/2021/02/02/m1-mac-mini-in-the-cloud/
  - CalChris 5y ago
    That’s the Mini. That’s not the M1.
    - rdsnsca 5y ago
      The Mini has an M1 cpu
      - CalChris 5y ago
        No, the Mac Mini available on AWS does NOT have an M1. It has an Intel Core i7. https://aws.amazon.com/ec2/instance-types/mac/ https://aws.amazon.com/ec2/instance-types/mac/
        enos_feedler 5y ago
        It has been said AWS will add M1.
dkjaudyeqooe 5y ago
ARM is the present, RISC-V is the future and Intel is the past. The magic of Apple's M1 comes from the engineers who worked on the CPU implementation and the TSMC process. The architecture has some impact on performance but I think it is simplicity and and ease of implementation that factors most into how well it can perform (as per the RISC idea). In that sense Intel lags for small, fast and efficient processors because their legacy architecture pays a penalty for decoding and translation (into simpler ops) overhead. Eventually designs will abandon ARM for RISC-V for similar reasons as well as financial ones. Really, today it's a question of who has the best implementation of any given architecture.
mr_toad 5y ago
> I used to think that ARM was really only suited for smaller devices. The current fastest supercomputer uses ARM. https://en.wikipedia.org/wiki/Fugaku_(supercomputer) https://en.wikipedia.org/wiki/Fugaku_(supercomputer)

by lprd 5y ago

fulafel 5y ago

The instruction set doesn't make a significant difference technically, the main things about them are monopolies (patents) tied to ISAs, and sw compatibility.

rvanlaar 5y ago
I'm interested in your thoughts on why this doesn't make a significant difference. From what I've read, the M1 has a lot of tricks up its sleeve that are next to impossible on X86. For example ARM instructions can be decoded in parallel.
- fulafel 5y ago
  Instruction decoding is more power efficient on arm, but x86 has solved it as a perf bottleneck, with the trace/uop caches and by doing some speculative work in the decoders. (Parallel decoding is also old hat and not a M1 or ARM land invention, it's trivial with RISC style insn format.). What other tricks do you have in mind? More broadly, as to why the ISA doesn't make a big difference: The major differences are at the microarchitecture level since OoO processors have such flexible dataflow machinery in them that you can kind of view the frontend as compiler technology. x86 and ARM are decades-old ISAs that have seen a many many rounds of iteration in form of added instructions and even backwards incompatible reboots at the 64-bit transition points so most hinderances have been fixed. In the olden days ISAs were important because processors were orders of magniture simpler, and instructions were processed as-is very statically (to the point that microarchitectural artifacts like branch delay slots were enshrined in some ISAs). This meant that eg the complexity of individual instructions could a bottleneck to how fast a chip could be clocked. Or in CISC land your ISA might have been so complex that the CPU was a microcoded implementation of the ISA and didn't have any hardwired fast instructions...

mhh__ 5y ago

The next decade is ARM's for the taking, but if Intel and AMD can make good cores then it's not anywhere close to slam dunk. One of the reasons why M1 is good is pure and simple that it has a pretty enormous transistor budget, not solely because it's ARM.

tambourine_man 5y ago
>…is pure and simple that it has a pretty enormous transistor budget There's a lot of brute force, yes, but it's not the only reason. There are lots of smart design decisions as well.
- mhh__ 5y ago
  "One of the reasons" I did say.
  - tambourine_man 5y ago
    True, I misread it.
- amelius 5y ago
  Yes, but those decisions optimize for the single user laptop case, not for e.g. servers.
api 5y ago
Being ARM has something to do with it. The x86 instruction decoder may be only about ~5% of the die, but it's 5% of the die that has to run all the time. Think about how warm your CPU gets when you run e.g. heavy FPU loads and then imagine that's happening all the time. You can see the power difference right there. It's also very hard to achieve more than 4X parallelism (though I think Ice Lake got 6X at some additional cost) in decode, making instruction level parallelism harder. X86's hack to get around this is SMT/hyperthreading to keep the core fed with 2X instruction streams, but that adds a lot more complexity and is a security minefield. Last but not least: ARM's looser default memory model allows for more read/write reordering and a simpler cache. ARM has a distinct simplicity and low-overhead advantage over X86/X64.

bitwize 5y ago

> So is ARM the future at this point? The near future. A few years out, RISC-V is gonna change everything.

kllrnohj 5y ago

It will come down entirely to who can sustain a good CPU core. Currently Apple is the only company making performance-competitive ARM cores that can make a reasonable justification for an architecture switch. Otherwise AMD's CPUs are still ahead of everyone else, including all other ARM CPU cores not made by Apple. And even Intel is still faster in places where performance matters more than power efficiency (eg, desktop & PC gaming)

floatboth 5y ago
Arm's Neoverse cores are doing pretty well in the datacenter space — on AWS, the Graviton2 instances are currently the best ones for lots of use cases. It's clear that core designs by Arm are really good. The problem currently is the lag between the design being done and various vendors' chips incorporating it. upd: oh also in the HPC world, Fujitsu with the A64FX seems to be like the best thing ever now
- rubatuga 5y ago
  Fujitsu flying under the radar while having the fastest cpu ever made haha
- kllrnohj 5y ago
  Graviton2 is competitive sometimes with Epyc, but also falls far behind in some tests (eg, Java performance is a bloodbath). Overall across majority tests, Neoverse consistently comes up short of Milan even when Neoverse is given a core-count advantage. And critically the per-core performance of Graviton2 / Neoverse is worse, and per-core performance is what matters to consumer space. But it can't just be competitive it needs to be significantly better in order for the consumer space to care. Nobody is going to run Windows on ARM just to get equivalent performance to Windows on X86, especially not when that means most apps will be worse. That's what's really impressive about the M1, and so far is very unique to Apple's ARM cpus. > oh also in the HPC world, Fujitsu with the A64FX seems to be like the best thing ever now A64FX doesn't appear to be a particularly good CPU core, rather it's a SIMD powerhouse. It's the AVX-512 problem - when you can use it, it can be great. But you mostly can't, so it's mostly dead weight. Obviously in HPC space this is different scenario entirely, but that's not going to translate to consumer space at all (and it's not an ARM advantage, either - 512bit SIMD hit consumer space via x86 first with Intel's Rocket Lake).

CalChris 5y ago

Apple isn't entering the cloud market. Moreover the M1 isn't a cloud cpu. The M1 SOC emphasizes low latency and performance per watt over throughput.

enos_feedler 5y ago
AWS has Mac mini, and is expected to add M1 mini into the mix [1]. I expect Apple to take lots of silicon design into data centers and edge computing. Over time I can see a lot of mobile apps running backend through Apple silicon with a full Apple cloud software stack to provide data management around security and privacy. 1. https://9to5mac.com/2021/02/02/m1-mac-mini-in-the-cloud/ https://9to5mac.com/2021/02/02/m1-mac-mini-in-the-cloud/
- CalChris 5y ago
  That’s the Mini. That’s not the M1.
  - rdsnsca 5y ago
    The Mini has an M1 cpu
    - CalChris 5y ago
      No, the Mac Mini available on AWS does NOT have an M1. It has an Intel Core i7. https://aws.amazon.com/ec2/instance-types/mac/ https://aws.amazon.com/ec2/instance-types/mac/
      - enos_feedler 5y ago
        It has been said AWS will add M1.

dkjaudyeqooe 5y ago

ARM is the present, RISC-V is the future and Intel is the past. The magic of Apple's M1 comes from the engineers who worked on the CPU implementation and the TSMC process. The architecture has some impact on performance but I think it is simplicity and and ease of implementation that factors most into how well it can perform (as per the RISC idea). In that sense Intel lags for small, fast and efficient processors because their legacy architecture pays a penalty for decoding and translation (into simpler ops) overhead. Eventually designs will abandon ARM for RISC-V for similar reasons as well as financial ones. Really, today it's a question of who has the best implementation of any given architecture.

mr_toad 5y ago

> I used to think that ARM was really only suited for smaller devices. The current fastest supercomputer uses ARM. https://en.wikipedia.org/wiki/Fugaku_(supercomputer) https://en.wikipedia.org/wiki/Fugaku_(supercomputer)