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When first launched, the Apple CPUs did about 50% more work per clock cycle (i.e. more instructions executed simultaneously) than the best Intel and AMD CPUs, e

When first launched, the Apple CPUs did about 50% more work per clock cycle (i.e. more instructions executed simultaneously) than the best Intel and AMD CPUs, enabling a 3.2 GHz Apple CPU to have the same single-thread speed as a 4.8 GHz Intel or AMD CPU. Because the power consumption grows at least quadratically with the clock frequency, having the same speed at a lower clock frequency provides better energy efficiency. Meanwhile, the difference in IPC (instructions per clock cycle) between Apple and the others has been reduced, but Apple still has a healthy advantage. The different microarchitecture explains the energy efficiency advantage for single-threaded tasks. On the other hand, for multi-threaded tasks, the power consumption per chip area is limited by cooling and the energy required to do a quantity of useful work (which is done by switching a certain number of logic gates) is mainly determined by the parameters of the CMOS process used to make the CPU die (assuming that the CPU designers are not incompetent). So for multi-threaded tasks the better energy efficiency of the Apple CPUs has been determined mostly by the fact that they have been the only company able to use the latest and greatest TSMC CMOS process.

KingOfCoders 2y ago
Apple jumped onto the split-core train early on. High performance cores for being good in IPC and low performance cores for multi core workloads with overall low power usage. Apple has the benefit of controlling the OS, so no scheduler problems. Intel came later but seems to make good advances, if you look at e-Cores in Lunar Lake. I predict AMD will go the same route (way bezond 5c), now that x86 also focuses on performance/watt and not peak performance (if you watch the announcements).
- adrian_b 2y ago
  Apple jumped onto the split-core train early on, because it was the first having access to more advanced manufacturing processes. CPUs with big and little cores were not useful for the old "14 nm" manufacturing processes used by Intel for Skylake and its derivatives, because in those processes the power consumption of a core and its speed could be varied in a very large range, e.g. for the extremes of the supply voltage, the clock frequency of a laptop CPU core could vary between 0.6 GHz and 4.5 GHz, corresponding to a variation of the power consumption per core of even 50 times. Modern processes have more constrained ranges for the optimal operating parameters of the transistors, so it has become better to split the cores into several classes that are designed with different trade-offs between power consumption and performance, instead of attempting to use the same core both at very low and at very high power consumptions. The decision to use 2 or more kinds of cores to cover the entire curve of performance vs. power consumption, when you can no longer cover it by varying the operating parameters of a single kind of core, is a no-brainer. While for the CPUs with a small number of cores, like for smartphones, tablets and light laptops, the existence of multiple kinds of cores is needed for optimum energy efficiency, the CPUs for desktops or big laptops with a great number of medium-size cores, like Raptor Lake, have them for a different reason. The big Intel cores, in the quest for maximum single-thread performance, have poor performance per chip area. The medium-size cores have better performance per area, so in the same limited chip area you can put more cores, increasing the multi-threaded performance beyond what would be obtained by filling the same area with big cores. Nevertheless, AMD has a better strategy than Intel, because their big cores with high single-thread performance and their "compact" cores with better performance per chip area are logically equivalent, avoiding the software incompatibility problems caused by Intel.
  - KingOfCoders 2y ago
    "Nevertheless, AMD has a better strategy than Intel" Only if it brings at least the same perf/watt results. We'll see what Lunar Lake vs. Strix does.

KingOfCoders 2y ago

Apple jumped onto the split-core train early on. High performance cores for being good in IPC and low performance cores for multi core workloads with overall low power usage. Apple has the benefit of controlling the OS, so no scheduler problems. Intel came later but seems to make good advances, if you look at e-Cores in Lunar Lake. I predict AMD will go the same route (way bezond 5c), now that x86 also focuses on performance/watt and not peak performance (if you watch the announcements).

adrian_b 2y ago
Apple jumped onto the split-core train early on, because it was the first having access to more advanced manufacturing processes. CPUs with big and little cores were not useful for the old "14 nm" manufacturing processes used by Intel for Skylake and its derivatives, because in those processes the power consumption of a core and its speed could be varied in a very large range, e.g. for the extremes of the supply voltage, the clock frequency of a laptop CPU core could vary between 0.6 GHz and 4.5 GHz, corresponding to a variation of the power consumption per core of even 50 times. Modern processes have more constrained ranges for the optimal operating parameters of the transistors, so it has become better to split the cores into several classes that are designed with different trade-offs between power consumption and performance, instead of attempting to use the same core both at very low and at very high power consumptions. The decision to use 2 or more kinds of cores to cover the entire curve of performance vs. power consumption, when you can no longer cover it by varying the operating parameters of a single kind of core, is a no-brainer. While for the CPUs with a small number of cores, like for smartphones, tablets and light laptops, the existence of multiple kinds of cores is needed for optimum energy efficiency, the CPUs for desktops or big laptops with a great number of medium-size cores, like Raptor Lake, have them for a different reason. The big Intel cores, in the quest for maximum single-thread performance, have poor performance per chip area. The medium-size cores have better performance per area, so in the same limited chip area you can put more cores, increasing the multi-threaded performance beyond what would be obtained by filling the same area with big cores. Nevertheless, AMD has a better strategy than Intel, because their big cores with high single-thread performance and their "compact" cores with better performance per chip area are logically equivalent, avoiding the software incompatibility problems caused by Intel.
- KingOfCoders 2y ago
  "Nevertheless, AMD has a better strategy than Intel" Only if it brings at least the same perf/watt results. We'll see what Lunar Lake vs. Strix does.