Ryan Smith at AnandTech has confirmed that the MacBook Air uses the Core i5-8210Y:
The i5-8210Y is one of Intel’s new Amber Lake-Y CPUs. Launched back in August, Amber Lake is Intel’s latest-generation 5W(ish) chips and goes under the 8th Gen Core branding. Compared to the Broadwell (5th Gen Core) chips in the previous MacBook Air, these chips represent a big step up in capabilities and performance, incorporating a newer CPU core design as well as a newer GPU design. However it’s also notable that the new chips, even in cTDP Up mode, are also much lower power than the older 15W U-series chips Apple used, which means that processor power consumption should be significantly reduced – and the chips thinner as well – though the total performance gain won’t be quite as much as if Apple had stuck with U-series chips.
As best as we can tell, the Core i5-8210Y is likely to be one of Intel’s “off roadmap” chips, which is an SKU that’s made at the behest of a single or small number of customers. These aren’t always publicly documented by the company, especially if it’s not going into a consumer device. There’s nothing particularly special about the 8210Y – it’s just clocked a bit differently than Intel’s standard chips – but for that reason I’m not immediately expecting that we’ll see it anywhere else. By the numbers then, the 8210Y is essentially an Amber Lake chip that’s permanently in cTDP Up mode, giving it a de facto 7W TDP. This improves the base clock speed to 1.6GHz. Meanwhile Apple trades some CPU turbo for some GPU turbo; the 3.6GHz CPU turbo is a bit lower than Intel’s standard i5 chip, however the 1.05GHz GPU turbo is 100MHz higher as a result.
I am trying to reserve judgement here until we see how the MacBook Air benchmarks compared to the MacBook and the MacBook Escape. In theory, it should be notably quicker than the 12-inch machine, thanks to the higher clock speed.