While the Surface Pro X can run native ARM64 apps in Windows 10 and 32-bit x86 app via emulation, it cannot run 64-bit x86 apps in emulation. That may change very soon according to a new report from Neowin. The publication says that although Qualcomm stated that 64-bit x86 emulation was never in the cards for its SoCs -- the SQ1 is an offshoot of the Qualcomm Snapdragon 8cx -- Microsoft and Qualcomm have in fact been working behind the scenes to make it a possibility.
Qualcomm was apparently sour on 64-bit emulation in the past due to performance concerns, but Microsoft likely sees support as necessary for the Windows on Arm to take off in the future. No one wants to buy a new $1,000+ device and find that out that a critical application that they use is not supported.
If and when this 64-bit x86 emulation comes to pass, it won't be able to offer the same performance as exiting 32-bit x86 emulation. In addition, Neowin adds that there are some tricky landmines for Microsoft to navigate here:
The way that typical installers work is that if your machine supports 64-bit, it delivers the 64-bit app. That's because in all current cases, 64-bit apps are equal or better than their 32-bit counterparts, at least in terms of performance. That will change for ARM though, where 32-bit apps will still offer a better experience.
It's an incredibly complex set of variables that Microsoft will have to work with here to get x86-64 emulation up and running, and this is probably why Qualcomm was reticent to jumping on board in the first place. With that being said, if Microsoft and Qualcomm can pull this off, it should simplify the app experience for Windows on Arm customers -- even if performance still isn't quite up to par with competing solutions.