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Power-performance is a very nonlinear curve, so it doesn't make sense to compare single-core TDPs with all-core TDPs. The iPhone XS is 2500 MHz when one core, b

Power-performance is a very nonlinear curve, so it doesn't make sense to compare single-core TDPs with all-core TDPs. The iPhone XS is 2500 MHz when one core, but drops to 2380 MHz when both primary cores are in use, a 5% performance drop... but this drop lowers power from 3.85 W to 2.12 W, 45% less! Hence it makes much more sense to treat the A series processors as 2 watt chips when looking at multi-core scores. They're targeting efficiently hitting these lower frequencies. You'll get a similar result for the 4800HS; it'll use a lot more than 4 W single-core.

kllrnohj 6y ago
I think you mean 2w cores not 2w chips? The A12X also cuts frequency when multiple are in use (as of course AMD and Intel CPUs do as well), but at 2w/core you're still talking 8w for a quad core, comparable in power to the quad core i5 in the current MacBook Air. The problem here is a severe lack of quality data. The best we have right now is SPEC2006 which is unfortunately only single core. You're absolutely right that it makes more sense to compare like for like in workloads, but we don't have any good multithreaded cross-platform benchmarks. There's geekbench, but it's somewhere between mediocre and shitty. And then nothing else? There's then no multithreaded benchmarks that also have measured power draw on an A12/A13. A 4800HS at it's 4w/core all core load is also still clocking higher than an A12X. When Apple has the thermal budget to spend as well they'd almost certainly do the same thing?
- Veedrac 6y ago
  Yes, 2 W/core. The difference is that at this power level, the A series chip will be a lot closer to peak performance than the Intel chip. > A 4800HS at it's 4w/core all core load is also still clocking higher than an A12X. This doesn't mean that much, since the range of efficient clock speeds depends on design choices, so they aren't always 1:1 comparable between architectures. Apple might well increase clock speed on their desktop chips, but unless it's only a few percent, it won't be as simple as pumping more power into the same dies; they have to actually redesign the core to operate efficiently at those higher speeds.

kllrnohj 6y ago

I think you mean 2w cores not 2w chips? The A12X also cuts frequency when multiple are in use (as of course AMD and Intel CPUs do as well), but at 2w/core you're still talking 8w for a quad core, comparable in power to the quad core i5 in the current MacBook Air. The problem here is a severe lack of quality data. The best we have right now is SPEC2006 which is unfortunately only single core. You're absolutely right that it makes more sense to compare like for like in workloads, but we don't have any good multithreaded cross-platform benchmarks. There's geekbench, but it's somewhere between mediocre and shitty. And then nothing else? There's then no multithreaded benchmarks that also have measured power draw on an A12/A13. A 4800HS at it's 4w/core all core load is also still clocking higher than an A12X. When Apple has the thermal budget to spend as well they'd almost certainly do the same thing?

Veedrac 6y ago
Yes, 2 W/core. The difference is that at this power level, the A series chip will be a lot closer to peak performance than the Intel chip. > A 4800HS at it's 4w/core all core load is also still clocking higher than an A12X. This doesn't mean that much, since the range of efficient clock speeds depends on design choices, so they aren't always 1:1 comparable between architectures. Apple might well increase clock speed on their desktop chips, but unless it's only a few percent, it won't be as simple as pumping more power into the same dies; they have to actually redesign the core to operate efficiently at those higher speeds.