Abstract: In a multiprocessor write-into-cache data processing system including: a memory; at least first and second shared caches; a system bus coupling the memory and the shared caches; at least one processor having a private cache coupled, respectively, to each shared cache; method and apparatus for preventing hogging of ownership of a gateword stored in the memory which governs access to common code/data shared by processes running in the processors by which a read copy of the gateword is obtained by a given processor by performing successive swap operations between the memory and the given processor's shared cache, and the given processor's shared cache and private cache. If the gateword is found to be OPEN, it is CLOSEd by the given processor, and successive swap operations are performed between the given processor's private cache and shared cache and shared cache and memory to write the gateword CLOSEd in memory such that the given processor obtains exclusive access to the governed common code/data.

Abstract: In a multiprocessor write-into-cache data processing system including: a memory; at least first and second shared caches; a system bus coupling the memory and the shared caches; at least one processor having a private cache coupled, respectively, to each shared cache; method and apparatus for preventing hogging of ownership of a gateword stored in the memory which governs access to common code/data shared by processes running in the processors by which a read copy of the gateword is obtained by a given processor by performing successive swap operations between the memory and the given processor's shared cache, and the given processor's shared cache and private cache. If the gateword is found to be OPEN, it is CLOSEd by the given processor, and successive swap operations are performed between the given processor's private cache and shared cache and shared cache and memory to write the gateword CLOSEd in memory such that the given processor obtains exclusive access to the governed common code/data.

Abstract: In order to reduce the size of the memory employed to store firmware, the firmware is written in virtual control words which are then reduced by allotting them to a primary control word memory and at least one secondary control word memory which is addressed by a field in the primary control word memory. A virtual set of secondary control words are each divided into a plurality of fields, and each field of each secondary virtual control word is marked as guarded or "don't care". If a field is marked as "don't care", the function represented by the virtual control word will perform properly no matter what the content of that field. Virtual control word pairs are then examined to ascertain if they can be combined into a single control word.

Abstract: A fault handling process in a computer system subject to CPU design errors and functioning under an operating system (OS) having an integral fault handling module includes the steps of: setting an intercept flag when a central processor fault occurs if the fault is to be directed to a preprocessor; establishing a safestore frame which includes information identifying the type of fault and whether the intercept flag is set; and transferring control to the OS fault handling module; then in the OS fault handling module, determining whether the intercept flag is set; if the intercept flag is not set, handling the fault in the OS fault module; if the intercept flag is set, transferring control from the OS fault module to an Intercept Process written in machine language; and handling the fault in the Intercept Process.

Abstract: In order to gather, store temporarily and deliver (if needed) central processor safestore information, a multiphase clock is employed to capture (one full clock cycle behind) the safestore information which typically includes all software visible registers in all (or selected) data manipulation chips of the CPU by routing the safestore information through temporary storage (under the influence of the multiphase clock) in a cache data array and into a special purpose XRAM module. Thus, upon the sensing of a fault, valid safestore information is available in the XRAM for analysis and, if appropriate, resumption of operation at a sequential point just previous to that at which the fault occurred.

Abstract: An apparatus and method correcting data groups within a data stream to form a corrected data stream and providing for selecting between the data stream and the corrected data stream as desired.