Abstract: A dual processor computer system includes a first processing system having a central processing unit which executes a series of data processing instructions, a data bus system for transferring data to and from the first central processing unit, a memory unit coupled to the first central processing unit, and a cross-link communications element for transferring data into and out of the first processing system. A similarly configured second processing system, operating independently of the first processing system, is also provided. The cross-link communications element associated with the second processing system is coupled to the cross-link communication element of the first processing system, for transferring data into the second processing system from the first processing system and for transferring data into the first processing system from the second computer system.

Abstract: Resets on a data processing system are targeted to specific locations of that processing system and have different effects. Some resets are transparent to instruction execution while other resets will interrupt the normal execution of instructions. In addition, in a multi-zone environment resets in one zone do not automatically propagate to the other zone; instead, each zone generates its own resets.

Abstract: A fault tolerant computer system has a central processing system which includes at least one set of data pathways, and executes a series of data processing instructions including the transfer of messages along the plurality of data pathways. At least one set of transaction data storage devices are coupled to the data pathways for storing a predetermined number of successive messages transferred most recently on the data pathways. Error checking devices are included for detecting the presence of errors in the central processing system. Error storage devices are coupled to the transaction data storage devices and the error checking devices for causing the transaction data storage devices to cease storing additional messages in response to the detection of errors by the error checking device.

Abstract: Method and apparatus for controlling initiating of bootstrap loading in a computer system having first and second discrete computing zones is disclosed. Each computing zone includes a status register for storing an operating system run (OSR) bit indicating that the zone has initiated bootstrap loading. A cable connects the computing zones to allow the first and second zones to read the status registers in the second and first zones, respectively. A CPU in each zone only enables initiation of bootstrap loading if the OSR bit in the other zone is not set.