[Teknoman117]

From the "roads not taken" perspective, Intel actually made something like a channel IO engine for the 8086/8088 family called the 8089 (https://en.wikipedia.org/wiki/Intel_8089) which supported the 20-bit address space of those systems and proper 8 and 16-bit operations. You could write little programs for it which would communicate with IO devices and respond to interrupts on either a shared or private bus, do some processing, and then move the results to main memory.

IBM in a cost saving move grafted the DMA engine from the 8080 family (the 8237) and made it mostly work by adding a page register to cover the remaining bits and setting one up in an odd way for the 286 to get it to do IO <-> memory transfers for 16-bit devices (but unable to do memory-to-memory transfers).