There’s a couple good reasons for a M1x using A14 cores. With new nodes, it takes time to get things right. A smaller chip is generally preferred as easier to

There’s a couple good reasons for a M1x using A14 cores. With new nodes, it takes time to get things right. A smaller chip is generally preferred as easier to work with and test. It also gives the node more time to stabilize so your big chips get better yields. Addressable market is another factor. There are over a billion iPhone users replacing devices every 1-3 years on average. There’s around 100 million Mac users as of 2018 replacing their computers every 5-8 years and that being split between 2 and 3 major market segments. That means making over 250 million A14 chips, but only around 15 million M1 chips (aside from iPads which are there to improve economies of scale by reducing two designs to one). The M1x probably addresses around 4.5 million computers and the M1p or whatever they call it probably addresses under a half million machines. A lot of people wanting the performance boost or fearing outdated, unsupported x86 machines will probably cause an increase in M1 demand, but that will be followed by a decreased demand for M2 and maybe even as far as M3 or M4 while demand catches up with the altered purchase cycle. Apple is no doubt well aware of this. In any case, it’s best to try a new node with a smaller part where you know you need a million wafers anyway. Once you’ve optimized and refined a couple steppings, you move to the larger chip with smaller demand where yields are worse in general. Personally, I think they would greatly benefit from a unified chiplet design starting with something close to the A14 then scaling up.