I don't think this is possible. It's certainly not desirable.

The closest you might be able to come is working to disable as much of the l1/l2/l3 caches, but I don't know if youncan do that in userland.

You might be able to do OS settings to run your cpu at a very low clock rate and pretend that's similar.

Even ancient chips like the 8088 and 6502 had some pipelining.