Why is the Intel(R) Core(TM) i7-7660U CPU @ 2.50GHz 2.50 GHz processor in my Surface Pro not supported by Windows11?

it's NOT about cores, or speed, or performance or anything like that.

it's all about an internal issue with the processor architecture for pre 8th gen...

In 2018 CPUs were affected by a serious design flaws that enabled the Spectre and Meltdown side-channel attacks. Microsoft had to release patches for Windows that slowed down PCs with older CPUs. This let Windows work around the security problems in these CPUs.

CPU manufacturers would have to rearchitect their older CPU designs to truly patch these security weaknesses. (and you know they won't)

Intel stated that Spectre and Meltdown were addressed with hardware level changes starting with Intel 8th-generation CPUs.

Isn’t it interesting that Windows 11 requires 8th-generation CPUs or newer? I would guess this is totally related. Of course, Microsoft isn’t screaming from the rooftops that PCs with older CPUs are fundamentally insecure at a hardware level compared to new devices. That wouldn’t be good for business. But it seems like Microsoft wants to quietly move everyone to new hardware so Microsoft knows it only has to support Windows 11 on CPUs with these security fixes.

Just a guess...

Hi Baskerfield, Hope you're doing well.

Microsoft has confirmed that Windows 11 will only officially support 8th Generations and newer Intel Core processors which is most likely because they have an integrated TPM 2.0(Trusted Platform Module) chip. I'm afraid if you've TPM 2.0 in your BIOS then only you can install windows 11 in your device.

However if you're very interested to use Windows 11, I can give you some registry tweaks to install it in your device:)

Windows 11 Supported Intel Processors 
https://learn.microsoft.com/en-us/windows-hardware/design/minimum/supported/windows-11-supported-intel-processors

Warm Regards