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I'm confused at this response. My thought is that instead of 32 high performance cores and 8 efficiency cores it might be better to have 8 high performance cor
by Symmetry 5y ago
I'm confused at this response. My thought is that instead of 32 high performance cores and 8 efficiency cores it might be better to have 8 high performance cores and ~100 efficiency ones which ought to be about the same area and power but provide a lot more throughput if software can utilize that level of parallelism.
There's a lot of software that won't scale to 108 cores, of course, but again I expect the amount of software that could usefully scale to 40 parallel threads but can't scale to 108 to be fairly small.
- bombcar 5y agoThe performance cores seem to take maybe twice as much space as the efficiency cores, so I'm not sure the tradeoff would be worth it - the efficiency cores would need to be more than half as fast taking into account the parallelism to make the tradeoff worth it. In a world where power and heat budgets don't matter at all you'd not have any efficiency cores, after all.
- Symmetry 5y agoThe general rule of thumb for reasonably sized cores, which both Apple's performance and efficiency cores are, is that performance tends to scale with the square of the transistor and energy budget due to N^2 structures like the bypass network, ROB, etc being the long poles. Now, for any given transistor budget there's going to be a non-linear tradeoff between performance and power governed by supply voltage versus process threshold voltage. And if you're testing a chip and using only one or the other of the two sorts of cores you're paying for the uncore and memory subsystem regardless of which cores you're testing which complicates things. But it would be really weird if power consumption wasn't super linear with performance, that's why "efficiency cores" have "efficiency" in their name.