## Input/Output Device Driver Reference

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### DMA Parallel Port Support

The OS/2 2.1 (and later) parallel port device driver for PS/2 systems supports DMA parallel ports using the ABIOS parallel port functions found on those system units.

Using the parallel port in a Programmed I/O (PIO) methodology causes the processor to be involved on each byte transmitted. This prevents the processor from performing other operations.

Using the parallel port in a DMA methodology causes the processor to be involved on each buffer transmitted. The larger the buffer, the fewer interrupts to the CPU, and the more time the CPU can spend doing other useful work.