CPUs have limited throughput, since there is a max frequency they can operate at, and a limit to the number of wires they can be connected to (throughput = no. of wires × frequency). Later designs of early computers increased the capability of computers by delegating more work to secondary chips.
Chipsets served as go-betweens in the AT form factor by IBM.
The ATX form factor also brought with it a new breed of computers with more specialised chipsets: the memory controller hub (MCH) and peripheral controller hub (PCH). The MCH coordinates high-throughput components, such as computer memory and graphics. The PCH specialises in lower-throughput needs.
Light takes 0.3 ns to travel 10 cm, approximately the distance by wire between the CPU and the MCH. This potentially causes operations between the CPU and MCH to slow down by one cycle, at frequencies above 3 GHz. One way the Intel Core i-series resolves this conundrum is to move the memory controller into the CPU.
A modern CPU is manufactured through a process called photolithography, by which the CPU components are etched onto the silicon substrate by successive layers of chemicals, masking, and laser exposure. When the CPU components could be made small enough, the MCH and CPU were designed onto the same chip, and this is the design used by the Intel Core i7 (1st-gen).
Slim laptops have been undergoing a gradual transition: more and more of their chips are no longer available as a replaceable card, but instead soldered directly to the mainboard. Since 2017/2018, most slim laptops pretty much have CPU, memory, storage, and network chips all soldered directly to the mainboard.
The M1 goes one step further: not only does it make do with fewer chips, it does so with passive cooling!
A system-on-chip (SoC) combines the core functionality of a system—processing, graphics, memory, and control—into a single chip package.
Around 2015, the high-performance computer industry quickly realised that this would be much more efficient if the CPU and GPU could share the same memory.
Shared memory is easier to implement when a company has control over the designs of both CPU and GPU.
The Apple A14 and Apple M1 are essentially the same chip architecture: they use almost the same building blocks, just with different numbers of them. On top of that, the Apple M1 implements unified memory, allowing the CPU and GPU (and other SoC components) to share the same system memory, greatly facilitating intra-chip communication.
Using the same hardware for both smartphones and laptops would make it much easier to write apps for both platforms. The closer they are in features, hardware, and software support, the easier things will be for developers.