Shuffle is different, it is not a foundational SIMD instruction, it is actually a good example of an extension that can be added later as an add-on that does no

Shuffle is different, it is not a foundational SIMD instruction, it is actually a good example of an extension that can be added later as an add-on that does not require a complete code rewrite. Whereas each of the MMX, SSE and AVX extensions was effectively a new instruction set, AND each had its own register set – 64, 128, 256 and 512 bit registers. Later generations (i.e. AVX2 and AVX-512) are better thought out, but, e.g. MMX – I do not think anyone uses it today, yet it is present in the silicon as the dead space. Prior art existed long before – Cray had vector instructions first, so it is not like Intel had to invent them from scratch.