iopaau —
Intel I/O Processor Application Accelerator Unit
iopxs* at mainbus?
iopaau* at iopxs?
The Application Accelerator Unit, or AAU, provides hardware-assisted support for
  performing block fills on a region of memory, XOR of multiple regions of
  memory (parity computation), and parity verification.
The iopaau driver supports the Application
    Accelerator Units on the following Intel I/O Processors:
  - Intel i80321 I/O Processor
The iopaau driver provides a back-end to
    the dmover(9) interface,
    and supports the following
    dmover(9) functions:
  - zero
- Zero a region of memory
- fill8
- Fill a region of memory with an 8-bit value
- copy
- Copy a region of memory
- xor2
- Perform an XOR of 2 input streams
- xor3
- Perform an XOR of 3 input streams
- xor4
- Perform an XOR of 4 input streams
- xor5
- Perform an XOR of 5 input streams
- xor6
- Perform an XOR of 6 input streams
- xor7
- Perform an XOR of 7 input streams
- xor8
- Perform an XOR of 8 input streams
Theiopaau device first appeared in
  NetBSD 2.0.
Due to limitations in how scatter-gather is done by the AAU hardware, a given
  DMA segment must be the same length for the output stream and each input
  stream. The easiest way to achieve this is to ensure that all streams used in
  an AAU operation begin at the same offset into a page.