You release a new firmware that doesn't support the new CPU.

It took 3 paragraphs in for this article to make it clear that you would need to buy a new CPU to get 12-cores.

The modules of the microcontroller were designed independently and released as new CPUs could be tested.

In its 64-bit mode the new CPU was freed from the 31-bit addressing constraints of its predecessors.

This exploited the greater memory addressing capability of the new CPU to provide a more flexible multi-tasking environment.

However, the combination of a new CPU and motherboard mean that you should make sure your favorite distro is fully supported.

If you don't have enough, adding RAM can make more of a difference than getting a new CPU!

Many newer CPUs have mechanisms to make this harder, such as a no-execute bit.

About 98% of new CPUs produced each year are embedded.

In addition, customers would have to rewrite their programs to run on the new CPU, something customers often balked at.