In a way it did. Tandy offloaded every possible function onto the processor to lower part count and hence cost, resulting in the infamous bit banger serial port and the equally infamous high resolution mouse adapter, which made the CPU time the discharge of a capacitor to figure out where the mouse pointer was, so you learned quickly to keep the mouse at the top left, minimizing that time, unless absolutely necessary. DMA for disk I/O? Only with third party hardware.