The Micro Channel architecture provides for exception signaling using the CHCK signal. Initial use of the CHCK signal in the PS/2 line of products was asynchronous. With the new advanced uses of the Micro Channel and bus master adapters, which are able to execute multiple I/O-operations in burst mode, synchronous exception handling is needed in order to correctly associate an exception with the command that caused it.
The synchronous exception support within the Micro Channel architecture provides for activation of the CHCK signal in the same bus cycle that caused the exception. This simplifies the exception handling and provides increased system data integrity.