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In the System Programming Guide, Part 1 Chapter 3 MEMORY MANAGEMENT OVERVIEW

These two mechanisms (segmentation and paging) can be configured to support simple single-program (or singletask) systems, multitasking systems, or multiple-processor systems that used shared memory.

So, does that mean that Intel CPU do support cooperation with others Intel CPU ?
Similar as NVLink Bridge.

If so, why there is no motherboard with multiple Intel CPU onboard, there is just for Xeon but not for others.

Else to program this multiple-processor system, I think it's Intel OneAPI that can do that, similar as CUDA for NVIDIA GPU.

You can buy multi-CPU motherboards with AMD thread ripper CPUs. Although, you really don't need multi-CPU boards to develop SMP systems as it is enough to run those on multicore CPUs. The difference between multicore and multi-CPU is minimal.

Rukog wrote:So, does that mean that Intel CPU do support cooperation with others Intel CPU ?

Some of them do, some of them don't. There aren't any CPUs that support everything in the architecture manual!

Rukog wrote:If so, why there is no motherboard with multiple Intel CPU onboard, there is just for Xeon but not for others.

The additional logic required from CPU and board makes the system more expensive. Also, usual desktop workloads do not benefit that greatly from multi-CPU setups (especially not with the ready availability of multi-core CPUs).

So the market available is that for high-end servers, i.e. Xeons, where the customer does not care as much about the die price.