You might only be able to get 8-16MB/s max out of some of those old drives (especially pre-1994), so you probably aren't missing much.
edit: whoops, that's bytes not bits per second
edit: whoops, that's bytes not bits per second
It also bears pointing out these microcontrollers have built-in parallel memory interface buses, which are likely compatible with IDE (which is just ISA == the 8088/8086 parallel bus on a cable.) With DMA, ketchup and fries…