have been defined in the CompactFlash specification 2.0. Those are PIO modes 5 and 6. They are specific to CompactFlash. PIO Mode 5 A PIO Mode 5 was proposed with operation at 22 MB/s, but was never implemented on hard disks because CPUs of the time would have been crippled waiting for the hard disk at the proposed PIO 5 timings, and the DMA standard ultimately obviated it. While no hard disk drive was ever manufactured to support this mode, some motherboard manufacturers preemptively provided BIOS support for it. PIO Mode 5 can be used with CompactFlash cards connected to ATA via CF-to-ATA adapters. See also WDMA (computer) – single/multi-word DMA AT Attachment – ATA specification Input/output Interrupt List of device bandwidths CompactFlash References Input/output