I am actually currently working on a CPU that has an auxiliary unit with a 521-bit integer type (although many instructions are 512-bit). These have some inter

I am actually currently working on a CPU that has an auxiliary unit with a 521-bit integer type (although many instructions are 512-bit). These have some interesting effects, but I can't say they are tremendously useful for bit hacks, at least not at the cost of the hardware to support them. Multiplications of this size are a very costly operation, for example. Even an addition or a leading zero count is a significant area. Vector units are about as good as you will get for most of this stuff. This unit, by the way, is intended primarily for cryptography (521 is the length of a large mersenne prime). Cryptography operations are the only times I have ever seen an integer wider than 64 bits in the wild, and most people use bignum libraries. The same pressures apply to 128-bit cores. It will make a lot of hardware a lot bigger and more complicated.