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I’m all for investment in less power hungry chips. Even if it’s from Google (for a short period of time. Who knows how long these chips will be supported)

by xyst 3y ago

adrian_b 3y ago
Server CPUs are not power hungry. Only the CPUs used in desktops and workstations are power hungry. The server CPUs (including x86 like AMD Genoa/Bergamo) normally consume between 2 W and 4 W per core, the same as the big cores of the laptop or smartphone CPUs. A server CPU consumes hundreds of watts only because it has a very large number of cores, so it is equivalent with a very large number of smartphones or laptops collocated in the same box. In complete servers, there is a significant fraction of the power that is not consumed by the CPUs but by the many high-speed interfaces. That is unavoidable and it does not depend on the architecture of the CPUs. Any newly announced server CPU should be more efficient than those already in production, otherwise there would be few advantages in introducing it, but which core architecture is used does not have enough influence as to ensure that it will not be leapfrogged by whatever server CPU will be announced later, regardless of the core ISA. When Apple has switched to Arm it was able to improve the efficiency by using much lower clock frequencies than Intel. This was only an indirect effect of using the Arm ISA, because it makes much easier the concurrent decoding of a great number of instructions. For server CPUs, the Arm ISA cannot enable similar efficiency gains, because all server CPUs are already using the most efficient clock frequencies, in the range 2.5 to 3.5 GHz, so it is not possible to repeat an efficiency gain like in Apple M1, by reducing the clock frequency. All the cloud vendors have chosen Arm because it is the only ISA that can be currently used to design their own high-performance SoCs, not because it would provide efficiency gains over the Intel/AMD cores. The overall efficiency of a custom SoC will indeed be better, because it is streamlined for their specific system architecture, in comparison with a general-purpose CPU from Intel, AMD or Ampere.

I’m all for investment in less power hungry chips. Even if it’s from Google (for a short period of time. Who knows how long these chips will be supported)

by xyst 3y ago

I’m all for investment in less power hungry chips. Even if it’s from Google (for a short period of time. Who knows how long these chips will be supported)

adrian_b 3y ago

Server CPUs are not power hungry. Only the CPUs used in desktops and workstations are power hungry. The server CPUs (including x86 like AMD Genoa/Bergamo) normally consume between 2 W and 4 W per core, the same as the big cores of the laptop or smartphone CPUs. A server CPU consumes hundreds of watts only because it has a very large number of cores, so it is equivalent with a very large number of smartphones or laptops collocated in the same box. In complete servers, there is a significant fraction of the power that is not consumed by the CPUs but by the many high-speed interfaces. That is unavoidable and it does not depend on the architecture of the CPUs. Any newly announced server CPU should be more efficient than those already in production, otherwise there would be few advantages in introducing it, but which core architecture is used does not have enough influence as to ensure that it will not be leapfrogged by whatever server CPU will be announced later, regardless of the core ISA. When Apple has switched to Arm it was able to improve the efficiency by using much lower clock frequencies than Intel. This was only an indirect effect of using the Arm ISA, because it makes much easier the concurrent decoding of a great number of instructions. For server CPUs, the Arm ISA cannot enable similar efficiency gains, because all server CPUs are already using the most efficient clock frequencies, in the range 2.5 to 3.5 GHz, so it is not possible to repeat an efficiency gain like in Apple M1, by reducing the clock frequency. All the cloud vendors have chosen Arm because it is the only ISA that can be currently used to design their own high-performance SoCs, not because it would provide efficiency gains over the Intel/AMD cores. The overall efficiency of a custom SoC will indeed be better, because it is streamlined for their specific system architecture, in comparison with a general-purpose CPU from Intel, AMD or Ampere.