Are you talking about sleepers, or just big lumps of tanalised wood from the garden centre?
I did a raised bed with real sleepers a couple of years ago with a half lap joint (but with sleepers on edge for height) drilled through and pinned to hold the joint together and into the ground to hold it in place.
To cut that joint I used a circular saw from each side, which left a bit in the middle uncut – the first joint I finished the cut with a handsaw, the remainder got a smack with a sledgehammer!
Bear in mind, the hard part was not cutting, but dealing with the years of creosote soaked into the wood and the weight of the things.
You won’t be lifting them onto a table saw easily – my workbench was the lawn and a few blocks of wood to prop one end of them off the grass.