5 ms·

I am far from an expert on this... but. For most software, can ARM realistically replace Intel? If we ignore the obvious advantages of the intrinsic instructi

by cjhanks 10y ago

I am far from an expert on this... but. For most software, can ARM realistically replace Intel? If we ignore the obvious advantages of the intrinsic instructions found in most Intel chips... Intel has a really solid and reliable clock speed with a relatively small number of steady states (low power, turbo, default). In my limited experience, ARM chips seem to have variable clock speeds depending on both the type (floating point/integer) and magnitude (number of cycles/sec) load. Is this only apparent in the IoT space? Does it disappear in ARM chips designed for servers? Am I delusional about this? It is really difficult to understand just how sensitive any given application is to the monotonic clock. Can most applications really just be ported?

james_a_craig 10y ago
To cut a long story short: Yes, most applications can just be ported. The number of applications that rely on the actual clock rate being steady is extremely close to zero. Bear in mind nearly everything runs fine on laptop machines, which generally have a much wider range of clock states, and have no problems. Similarly, each core in modern machines is likely to be running at a different speed, and again, no problems. Finally, the clock rates used are a matter of OS policy; if you tell your OS to keep the CPU at a particular speed, it'll do it, regardless of whether it's an x86 or an ARM CPU.
- nickpeterson 10y ago
  I'm struck by how hard it would be to track down a bug that depends on the consistency of the clockrate...
  - koffiezet 10y ago
    Bugs like the ones you describe come down to timing. But it's not like "the old days" where for a specific target, there was only 1 chip/clockspeed so devs simply relied on it for timing since an RTC was or not available, or too slow to access. These days, it would be very hard to actually write code that relies on a specific clock-rate and work reliably. It's a lot easier and reliable to use the clock for time-sensitive stuff.

by cjhanks 10y ago

james_a_craig 10y ago

To cut a long story short: Yes, most applications can just be ported. The number of applications that rely on the actual clock rate being steady is extremely close to zero. Bear in mind nearly everything runs fine on laptop machines, which generally have a much wider range of clock states, and have no problems. Similarly, each core in modern machines is likely to be running at a different speed, and again, no problems. Finally, the clock rates used are a matter of OS policy; if you tell your OS to keep the CPU at a particular speed, it'll do it, regardless of whether it's an x86 or an ARM CPU.

nickpeterson 10y ago
I'm struck by how hard it would be to track down a bug that depends on the consistency of the clockrate...
- koffiezet 10y ago
  Bugs like the ones you describe come down to timing. But it's not like "the old days" where for a specific target, there was only 1 chip/clockspeed so devs simply relied on it for timing since an RTC was or not available, or too slow to access. These days, it would be very hard to actually write code that relies on a specific clock-rate and work reliably. It's a lot easier and reliable to use the clock for time-sensitive stuff.