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adrian_byesterday at 10:25 PM1 replyview on HN

Besides the fact that Lunar Lake has a lower consumption in the memory interface, which has nothing to do with the fabrication process, single-thread benchmarks cannot be used to compare CPU fabrication processes.

Both the absolute performance and the performance per watt in single-thread benchmarks are determined mainly by the CPU design and they are only slightly constrained by the CPU fabrication process.

Only the multithreaded benchmarks are useful for comparing CMOS fabrication processes, because the performance in multithreaded benchmarks (with a given cooling system) is limited mainly by the energy required to switch a logic gate, which is a characteristic of the fabrication process, and they are only weakly dependent on the CPU design, as long as the CPU design does not have obvious mistakes.

In multithreaded benchmarks, CPUs work at a fixed power consumption, determined by the maximum allowable temperature and the cooling system. A fixed power means a fixed number of gates that switch per second. The completion of a given benchmark requires a similar number of gate switchings in well designed CPUs, in which case the performance in such a benchmark is fully determined by the fabrication process. Deviations from proportionality appear when some CPUs need much less gate switchings than others to complete some work, which happens for example when a CPU has wider vector or matrix execution units, e.g. by supporting AVX-512 or SME or AMX.


Replies

aurareturnyesterday at 10:53 PM

On package memory disproportionally affects idle power consumption more than load. In Cinebench 2024, which is a heavy load test, on package memory likely makes little difference.

ST is far better than MT for this node comparison. MT is heavily influenced by core count, clock speed, core configuration. Panther Lake also has 3 tiers of cores compared to Arrow Lake's 2. The architecture for MT is entirely different.

Meanwhile, for ST, a core is a core. It's less or not affected by architectural changes to core configurations.