Abstract: A host data processing system operating under the control of a host operating system such as an enhanced version of the UNIX operating system on a RISC based hardware platform includes an emulator which runs as an application process for executing emulated system (ES) user application programs. The emulator includes a number of emulated system executive service components including a socket command handler unit and a socket library component operating in shared memory and an interpreter, an emulator monitor call unit (EMCU) and a number of server components operating in host memory. The host operating system further includes a host socket library interface layer (API) which operatively connects through a TCP/IP network protocol stack to the communications facilities of the hardware platform. The socket server components operatively connect ES TCP/IP application programs to the socket library interface layer of the host operating system when such application programs issue standard ES socket library calls.

Abstract: A host data processing system which includes a plurality of input/output devices operates under the control of an enhanced version of the UNIX operating system. The host system includes an emulator which runs as an application process for executing user emulated system (ES) application programs. The emulator includes a number of emulated system executive service components operating in shared memory and an interpreter, an emulator monitor call unit (EMCU) and a number of server facilities operating in the host memory. The ES executive service command handler component is extended to accommodate a number of dual decor commands which invoke host system facilities to execute terminal based commands either synchronously or asynchronously through the automatic creation of host shell mechanisms directly accessible by emulated system users. The server facilities include a network terminal driver (NTD) server for executing emulated system user terminal requests through host system drivers.

Abstract: A data processing system is disclosed in which a plurality of central processing units have access to all the system resources, i.e., have a peer relationship. During initialization of the data processing system, all the system resources are allocated to the individual central processing units according to a preselected distribution procedure, the identification of available resources thereafter being stored in the files of the individual central processing units. During the operation of the data processing system, the resources can be reallocated by a predetermined procedure. The central processing units entering such a relationship are required to include apparatus and/or software procedures that prevent access to system resources not assigned thereto. A mail box procedure, using locations in the main memory unit permit communication between the central processing units and are used in the dynamic allocation of resources.

Abstract: In a data processing system having a plurality of non-homogeneous central processing units, apparatus is disclosed that permits a central processing unit not having mechanisms for protection of the allocation of resources to be coupled to the data processing system while preserving a peer relationship among the central processing units. The protection apparatus is interposed between the coupled central processing unit and the system bus and reviews each access to data processing system resources to insure that the accessed system resource is available to the associated data processing system. In addition, the apparatus permits initialization procedures without interprocessor conflict, provides status information from the coupled central processing unit to a requesting central processing unit and permits selected control signals to be applied to the coupled central processing unit.

Abstract: A data processing system includes a logical address to a physical address translator in an extended memory management unit. A 128 word memory stores task segment descriptor words which include a base address. A 16 word memory stores corresponding present bits to indicate if the addressed task segment descriptor is present in its memory. This arrangement allows a 128 word memory to be cleared in 16 memory cycles.

Abstract: A data processing system includes a central processor unit (CPU), a main memory and a memory management unit (MMU). Information is stored in main memory in segments, each segment being identified by a segment descriptor stored in a translation table in the MMU. Logical addresses from the CPU address segment descriptors in the MMU's translation table. These segment descriptors include the physical address of the location in main memory of the first word of the segment. If the segment descriptor is not in the translation table location, then the MMU operation is suspended while the segment descriptor is demand fetched from main memory.

Abstract: The directory and cache store of a multilevel set associative cache system are organized in levels of memory locations. Round robin replacement apparatus is used to identify in which one of the multilevels information is to be replaced. The directory includes parity detection apparatus for detecting errors in the addresses being written in the directory during a cache memory cycle of operation. Control apparatus combines such parity errors with signals indicative of directory hits to produce invalid hit detection signals. The control apparatus in response to the occurrence of a first invalid hit detection signal conditions the round robin apparatus as well as other portions of the cache system to limit cache operation to those sections whose levels are error free thereby gracefully degrading cache operation.

Abstract: In a system which includes a common bus to which a plurality of units are connected for the transfer of information, such as a data processing system, information may be transferred by the highest priority unit during an asynchronously generated bus transfer cycle. Logic is provided for enabling a first unit, such as a central processor, to make a multiple fetch request of a second unit, such as a memory, during a first transfer cycle. The multiple fetch request requests the second unit to transfer multiple parts of data to the first unit during multiple further transfer cycles, wherein one part of data is transferred in each further transfer cycle. Logic is provided in the second unit to enable the second unit to indicate to the first unit, except during the last further transfer cycle, that each further transfer cycle will be followed by another further transfer cycle.

Abstract: In a system which includes a common bus to which a plurality of units are connected for the transfer of information, such as a data processing system, information may be transferred by the highest priority requesting unit during an asynchronously generated bus transfer cycle. Logic is provided for enabling a multiple fetch operation in which the master unit requesting multiple words of information from the slave unit during a first bus transfer cycle may receive such information from the slave unit during a series of later slave generated bus cycles. Logic is provided for enabling any other units to communicate over the common bus during the time between the first cycle and such last cycle during which the slave unit responds, thereby enabling at least two pairs of units to communicate with each other respectively, in an interleaved manner.

Abstract: In a system which includes a common bus to which a plurality of units are connected for the transfer of information, such as a data processing system, information may be transferred during asynchronously generated information transfer cycles. Logic is provided for enabling a first unit to transfer first information to a second unit during a first request transfer cycle requesting that the second unit transfer second information to the first unit during a later first response transfer cycle. Logic is also provided to enable the first unit to transfer third information to a third unit during a second request transfer cycle requesting that the third unit transfer fourth information to the first unit during a later second response transfer cycle. Logic is provided that enable the first unit to transfer the third information before receiving the second information and logic is further provided that enables the first unit to receive the second information before or after receiving the fourth information.

Abstract: A host system includes a microprogrammed processing unit which couples a foreign processing unit to the main memory of the host system. The microprogrammed processing unit also couples to an interface connected to the foreign processor. During operation, the host processor transfers a channel command to the microprogrammed processing unit which is operative under firmware control to perform the various control functions required for initiating a particular job. In this manner, the various parameters and information necessary to dispatch a job of the foreign processor is accomplished expeditiously under the firmware control in response to commands issued by the host processor.

Abstract: In a data processing system having independently operating asynchronous processors, apparatus is disclosed which provides for interprocessor synchronization and/or information exchange. Synchronization interlocks and controls are provided for both identifying shared resources of a control processor and an input/output controller (IOC) processor and for obtaining control over these shared resources. If a conflict situation for any one of the shared resources arises, apparatus is disclosed whereby the IOC processor is provided the capability of assuming control over the shared resource even though the central processor has control over it. One of the shared resources is an interprocessor communication register which allows communication of control information between both the central processor and the IOC processor and from the central processor to the peripheral processor over a shared bus.