Originally Posted by
MemberBerry
With modern CPUs the I/O ports are on the same bus as the memory. The instruction set is backwards compatible so old software can still work the same way as before. However the modern architecture supports a new feature: I/O devices can read and write directly from/to memory, bypassing the CPU, which can be a huge benefit reducing CPU load during large I/O operations.
This is not a new feature, it was available on the PDP11 way back in the eighties when I was an FE on DEC hardware!