.i? (IOS Debug Binary Utility)

Help menu for IOS commands:

.IDCB <addr> Dumps I/O Subsystem Device Control Block structure.

.IIOP <addr> Dumps I/O Subsystem I/O Packet structure.

.IMED Dumps I/O Subsystem Memory Element Descriptor structures.

.IDV (DISKVSD debug binary also required) Display disk calldown/callup statistics

.ISAPNP Display current read data port, followed by information about each ISA bus card (if any).