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Why on earth would we want to converge on ARM? The first ARM architecture that was somewhat palatable was ARMv7, everything before that an unusable mess of diff

Why on earth would we want to converge on ARM? The first ARM architecture that was somewhat palatable was ARMv7, everything before that an unusable mess of different chips with vastly different capabilities. Their extensions are bad (read: subtly incompatible) late copies of what Intel and AMD are driving. Most of the innovation happens not at ARM, but their respective licensees. It took others inventing EFI to get some form of BIOS-equivalent for ARM, but even today the company gives the impression that they couldn't care less.

luxurycommunism 6y ago
Someone finally talking sense here.
pjmlp 6y ago
The Intel hate is so big that ARM fans don't acknowledge what they will lose in the process.
petre 6y ago
I just wonder what implications is the Arm sale to Nvidia going to have on Apple, who is switching their MacOS hardware from Intel to Arm.
- claudeganon 6y ago
  Hopefully MacBooks will be able to have GPUs that aren’t pitiful and outdated?
- ksec 6y ago
  Apple owns a perpetual ARMv8.2 license. And since they work closely with ARM on ARMv9 they might already have a license for that as well. Basically doesn't concern Apple at all.
  - saagarjha 6y ago
    Apple is already shipping devices with ARMv8.4; do they need a specific license for that?
freeone3000 6y ago
Because the ISA is simple, the perf/watt is way better, and we're reaching the point where architecture-specific native code is not explicitly sought out by most users, so we can actually change processors.
- saagarjha 6y ago
  Most users however do depend quite a bit on the performance of a small section of architecture-specific code.
  - freeone3000 6y ago
    (I'm going to exclude Linux in the below, because it's an odd duck where users/distributors can reasonably be expected to recompile every program they use for a new architecture.) Sure! But that code is generally core OS code written by a small number of people and deployed widely. If Apple or Microsoft or Google decided that OpenPOWER was the way to go, we'd be able to switch over at least some use cases. ALL of the above have current Arm offerings. Arm has reached "good enough" performance - the snapdragon 855 is as fast as a i5-8630U, and uses half the power. The primary barrier to processor migration is compatibility with user-mode programs. Since the vast majority of programs are now using primarily ILs, such as JS or C#, once the runtimes are ported (and they have been), there's not a lot of lasting incompatibility since programs bind to APIs, not ISAs. Apps for Work (CAD, Photoshop, dev tools) are traditionally the last to port, but there has been no better time to switch architectures than now, and it's only getting easier.
    - saagarjha 6y ago
      As someone going through a processor migration right, now, the core OS is actually not that hard to move. But even once you change all the language runtimes, there's a fair bit of proprietary software (including games) that are unlikely to move quickly.
adrian_b 6y ago
I agree with what you said, but there is a reason for wanting to converge on ARM. There exists no good alternative. ARMv8.2 or newer is a very well designed ISA, while RISC-V is a very bad ISA and I would hate to be forced to use it. OpenPOWER is a far better ISA than RISC-V, but unfortunately most developers do not have any experience with POWER and they have the wrong belief that POWER is some antique ISA while RISC-V must be some modern fashionable ISA. Therefore even if OpenPOWER is much better, it is less likely than RISC-V to be used as a replacement for ARM. I and probably thousands of other engineers could design a much better ISA than RISC-V in a week of work, but no one of the creators of those thousands of new ISA variants would be able to convince all the other people to choose his/her variant over the others and start the significant amount of work needed for porting all the required software tools, e.g. LLVM and gcc. So, if ARM would no longer be an acceptable choice, I do not see any hope that its replacement would not be greatly inferior.
- robot 6y ago
  I am actually pretty curious to see a demo of features from you that backs up that RISC-V is bad and Open Power is much better. What convinced me was how thin the RISC-V book[1] is, and I have seen both ARM and Intel reference manuals. For example the V extension removes need to specify data size, greatly reducing instructions needed. I have no idea about Open Power btw. [1] http://riscvbook.com/ http://riscvbook.com/ P.S. I am hiring U.S. candidates for ARMv8, x86 roles: https://careers.vmware.com/main/jobs/R2009422?lang=en-us https://careers.vmware.com/main/jobs/R2009422?lang=en-us
  - saagarjha 6y ago
    While I’m not really an expert on either, I have looked at code for both and I got the impression that RISC-V’s “simplicity” is actively harmful to making it a good ISA outside of teaching because it’s instructions are just not really all that great; indexing into an integer array (for example) is a shift, add, then load while basically every other architecture can do this in one instruction. It seems to me that the ISA is really designed more towards being pretty than being practical.
- 6y ago

luxurycommunism 6y ago

Someone finally talking sense here.

pjmlp 6y ago

The Intel hate is so big that ARM fans don't acknowledge what they will lose in the process.

petre 6y ago

I just wonder what implications is the Arm sale to Nvidia going to have on Apple, who is switching their MacOS hardware from Intel to Arm.

claudeganon 6y ago
Hopefully MacBooks will be able to have GPUs that aren’t pitiful and outdated?
ksec 6y ago
Apple owns a perpetual ARMv8.2 license. And since they work closely with ARM on ARMv9 they might already have a license for that as well. Basically doesn't concern Apple at all.
- saagarjha 6y ago
  Apple is already shipping devices with ARMv8.4; do they need a specific license for that?

freeone3000 6y ago

Because the ISA is simple, the perf/watt is way better, and we're reaching the point where architecture-specific native code is not explicitly sought out by most users, so we can actually change processors.

saagarjha 6y ago
Most users however do depend quite a bit on the performance of a small section of architecture-specific code.
- freeone3000 6y ago
  (I'm going to exclude Linux in the below, because it's an odd duck where users/distributors can reasonably be expected to recompile every program they use for a new architecture.) Sure! But that code is generally core OS code written by a small number of people and deployed widely. If Apple or Microsoft or Google decided that OpenPOWER was the way to go, we'd be able to switch over at least some use cases. ALL of the above have current Arm offerings. Arm has reached "good enough" performance - the snapdragon 855 is as fast as a i5-8630U, and uses half the power. The primary barrier to processor migration is compatibility with user-mode programs. Since the vast majority of programs are now using primarily ILs, such as JS or C#, once the runtimes are ported (and they have been), there's not a lot of lasting incompatibility since programs bind to APIs, not ISAs. Apps for Work (CAD, Photoshop, dev tools) are traditionally the last to port, but there has been no better time to switch architectures than now, and it's only getting easier.
  - saagarjha 6y ago
    As someone going through a processor migration right, now, the core OS is actually not that hard to move. But even once you change all the language runtimes, there's a fair bit of proprietary software (including games) that are unlikely to move quickly.

adrian_b 6y ago

I agree with what you said, but there is a reason for wanting to converge on ARM. There exists no good alternative. ARMv8.2 or newer is a very well designed ISA, while RISC-V is a very bad ISA and I would hate to be forced to use it. OpenPOWER is a far better ISA than RISC-V, but unfortunately most developers do not have any experience with POWER and they have the wrong belief that POWER is some antique ISA while RISC-V must be some modern fashionable ISA. Therefore even if OpenPOWER is much better, it is less likely than RISC-V to be used as a replacement for ARM. I and probably thousands of other engineers could design a much better ISA than RISC-V in a week of work, but no one of the creators of those thousands of new ISA variants would be able to convince all the other people to choose his/her variant over the others and start the significant amount of work needed for porting all the required software tools, e.g. LLVM and gcc. So, if ARM would no longer be an acceptable choice, I do not see any hope that its replacement would not be greatly inferior.

robot 6y ago
I am actually pretty curious to see a demo of features from you that backs up that RISC-V is bad and Open Power is much better. What convinced me was how thin the RISC-V book[1] is, and I have seen both ARM and Intel reference manuals. For example the V extension removes need to specify data size, greatly reducing instructions needed. I have no idea about Open Power btw. [1] http://riscvbook.com/ http://riscvbook.com/ P.S. I am hiring U.S. candidates for ARMv8, x86 roles: https://careers.vmware.com/main/jobs/R2009422?lang=en-us https://careers.vmware.com/main/jobs/R2009422?lang=en-us
- saagarjha 6y ago
  While I’m not really an expert on either, I have looked at code for both and I got the impression that RISC-V’s “simplicity” is actively harmful to making it a good ISA outside of teaching because it’s instructions are just not really all that great; indexing into an integer array (for example) is a shift, add, then load while basically every other architecture can do this in one instruction. It seems to me that the ISA is really designed more towards being pretty than being practical.
6y ago