As someone who recently ordered a 2020 iPad Pro and still haven't received it, I'm eager to find out how A12Z compares against A14.
Since there's no benchmark on A14 yet, I did some calculations on existing benchmarks and Apple's spec.
A14 consists of a 6-core CPU and a 4-core GPU, and A12Z is 8-core + 8-core.
Apple says that A14 is 40% faster than A12 in terms of CPU, and 30% faster in terms of GPU. In comparison, according to
Geekbench, A12Z (iPad Pro 11 2nd gen) is about 60% faster on CPU multi-core performance and 120% faster on GPU performance (Metal) comparing to A12 (iPad Air 3rd gen).
The caveat is CPU single-core performance, assuming what Apple says about A14's CPU is multi-core, then A14's single-core performance is (1.4/6)/(1.6/8)-1 = 16.67% faster than A12Z, but in the meantime, A13 (iPhone 11 Pro)'s single-core performance is about 18.69% faster than A12Z, it would be odd if A14's single-core performance wasn't better than A13, let alone slower. So in the other case where what Apple meant was actually single-core performance, A14's multi-core performance would be 1.4*6/(1*8) - 1 = 5% faster than A12Z, (A12Z's single-core performance is nearly identical to A12), which makes a little bit more sense IMO.
When we talk about GPU performance we generally don't care about that of a single CU, so I think the "30% faster than A12" is the combined GPU performance.
In conclusion, my (very rough) estimation is:
- A14 GPU is about 40% slower than A12Z.
- A14 CPU single-core performance is 40% faster than A12Z, and multi-core performance is 5% faster.
or
- A14 CPU single-core performance is 17% faster than A12Z, and multi-core performance is 12.5% slower.