Intel had multiple years of promising that their new next-gen more efficient 10nm CPUs were coming very soon, and then those kept being delayed.
The chips they did release in that time period were mostly minor revisions of the same architecture.
Apple was pretty clearly building chassis designs for the CPUs that Intel was promising to release, and those struggled with thermal management of the chips that Intel actually had on the market. And Apple got tired of waiting for Intel and having their hardware designs out of sync with the available chips.
> and those struggled with thermal management of the chips
An ironic mirror of the PowerPC era when every version of the G5 was struggling with high power consumption and heat generation when operated at any competitive frequency/performance level. The top end models like the 2.5GHz quad-G5 needed water cooling, consumed 250W when idle, and needed a 1kW PSU.
Intel's offering at the time was as revolutionary as the M-series chips.
Yep, it was a very similar situation where Apple wanted to keep their hardware cadence but were beholden to a third party on the chip roadmap.
These days they're still somewhat beholden to TSMC continuing to make progress on nodes etc, but I think they have a closer partnership and a lot more insight into that roadmap so they can keep their hardware plans in sync.
The chips they did release in that time period were mostly minor revisions of the same architecture.
Apple was pretty clearly building chassis designs for the CPUs that Intel was promising to release, and those struggled with thermal management of the chips that Intel actually had on the market. And Apple got tired of waiting for Intel and having their hardware designs out of sync with the available chips.