In the last 15 years, we have seen a seismic shift in mainstream computing. In the 90s and early 00s, pretty much all computing was done on desktop and laptop PCs, with Intel and Windows commanding a near-monopoly of the market. The early 00s saw some competition from AMD, which Intel swiftly crushed through some rather criminal means. Apple moved to x86 CPUs in mid-00s, to complete domination of x86.
However, then came the smartphones, and with it, Arm staked its claim. Arm's model is quite a bit different from Intel or AMD. While Intel and AMD build, manufacture (well, AMD does outsource manufacturing now, but Intel still has an end-to-end solution), market and sell their own processors, Arm only designs the architecture and cores. Some manufacturers like Apple and Samsung just license the base Arm64 architecture and design their own cores, while others like Qualcomm license both Arm's architecture and Cortex cores. Of course, these are then manufactured by TSMC and Samsung chiefly.
Arm beat Intel, AMD, MIPS and other competitors to the mobile computing crown by focusing entirely on power efficiency. The downside, of course, was outright performance, where Intel and AMD are still far ahead. While we have seen stuff like Qualcomm Snapdragon 8cx focusing on higher performance, the core architecture was still based on Arm's power efficiency mantra. The only Arm licensee that has focused on increasing performance has been Apple, with ever more wider cores and higher performance that could theoretically rival Intel and AMD. Indeed, rumours now suggest Apple will introduce a MacBook with Arm processors next year, while the iPad Pros get ever more powerful.
Now, Arm is officially getting into the high-performance CPU core arena with Cortex-X. It's not quite as aggressive as Apple's brute-force approach - after all, no other company can command the insane margins they do. But it still gets Arm in the ballpark of Apple, AMD and Intel. Arm is also continuing its line of Cortex-A series, with the next iteration Cortex-A78, which offers the usual iterative gains we have become used to. The X1 core takes things further by offering a huge 30% performance uplift. Granted, power consumption is expected to go up by 50%, but that's an expected trade-off for chasing max performance. As a side-note, we also see an interesting scenario where the x86 and Arm CPUs are converging on both performance and power efficiency. There's no "inherent bloat" with x86 - it's just most x86 cores were following a different strategy.
The big question here is, of course, software. While I expect the highest-end Android smartphones and tablets to feature only 1 Cortex-X1 core, in combination with 3 Cortex-A78, this core was definitely built for PCs and workstations. We have seen Windows continue to work on Arm support, with 64-bit emulation for x86 apps coming later this year. A lot of the basic apps such as Google Chrome have now been ported for native Arm64 code, and performance has thus increased dramatically. Adobe has promised Creative Cloud, and other vendors are slowly but surely getting on board with Windows-on-Arm. ChromeOS and Linux also have expanding Arm support, while as mentioned above, macOS is likely to make the jump next year. At the same time, we are also seeing Arm carving a niche in some server markets.
There are some Windows laptops and convertibles already running on Arm - Surface Pro X and Samsung Galaxy Book S being the frontrunners. With the launch of Cortex X1, improved support for Arm on Windows over the years, I can definitely see many more ultraportable laptops move to Arm. What about gaming laptops and high-performance desktops/workstations? Yeah, those are going to be on Intel or AMD for years/decades to come. But Arm does not intend to replace x86 - just make in-roads into certain niches with mobile computing.
For more details, do check out AnandTech's in-depth article