Abstract: Timing facilities are used to provide sequence values that are unique across operating system images. A sequence value includes various components, including timing information and selected information. The selected information is used to provide a sequence value that is unique across a plurality of operating system images. Additionally, the sequence value can include, for instance, a processor identifier component and a placeholder component. The placeholder component ensures that the sequence value is an increasing value, even when the physical clock used to provide the timing information wraps back to zero.

Abstract: A method is disclosed for instructing a computing system to ensure that a line is present in an instruction cache that includes selecting a line-touch instruction, recognizing the line-touch instruction as a type of branch instruction where the branch is not taken, executing the line-touch instruction to fetch a target line from a target address into the instruction cache, and interlocking the execution of the line-touch instruction with the completion of the fetch of the target line in order to prevent execution of the instruction following the line-touch instruction until after the target line has reached the cache.

Abstract: An exemplary embodiment of the invention is a method and system for managing a result returned from a translator co-processor to a recovery unit of a central processor. The computer system has a pipelined computer processor and a pipelined central processor, which executes an instruction set in a hardware controlled execution unit and executes an instruction set in a milli-mode architected state with a millicode sequence of instructions in the hardware controlled execution unit. The central processor initiates a request to the translator co-processor a cycle after decode of a perform translator operation instruction in the millicode sequence. The translator co-processor processes the perform translator operation instruction to generate a perform translator operation result. The translator co-processor returns the results to a recovery unit of the central processor. The recovery unit stores the perform translator operation result in a system register.

Abstract: An exemplary embodiment of the present invention is a method and system for reducing the number of branch instructions required to test combinations of millicode branch points. The method is implemented via a pipe-lined computer processor executing a millicode routine. The processor interrogates a millicode condition code; interrogates a first field of the TMBP instruction, the results of which determine a logical function to be performed on the millicode condition code; interrogates a second field of the TMBP instruction which specifies a first millicode branch point; interrogates a third field of the TMBP instruction, which specifies a second millicode branch point; and sets a millicode condition code based upon the results of the interrogating and used for executing subsequent TMBP instructions or conditional branch instructions.

Abstract: A method is disclosed for instructing a computing system to ensure that a line is present in an instruction cache that includes selecting a line-touch instruction, recognizing the line-touch instruction as a type of branch instruction where the branch is not taken, executing the line-touch instruction to fetch a target line from a target address into the instruction cache, and interlocking the execution of the line-touch instruction with the completion of the fetch of the target line in order to prevent execution of the instruction following the line-touch instruction until after the target line has reached the cache.

Abstract: Timing facilities are used to provide sequence values that are unique across operating system images. A sequence value includes various components, including timing information and selected information. The selected information is used to provide a sequence value that is unique across a plurality of operating system images. Additionally, the sequence value can include, for instance, a processor identifier component and a placeholder component. The placeholder component ensures that the sequence value is an increasing value, even when the physical clock used to provide the timing information wraps back to zero.

Abstract: To support a new processor control bit, the Real Space Control (RSC) bit, in a processor system with an existing translation lookaside buffer, an existing control bit, the Private Space bit, in the translation lookaside buffer is redefined as an Ignore Common segment bit to create new non-overlapping translation lookaside buffer entries.

Abstract: A physical clock is expanded to enhance its precision. Existing instructions are capable of using the enhanced physical clock. Execution of an instruction begins, which places a value of the expanded physical clock in a physical clock field of a clock representation. The physical clock field is, however, unable to accommodate the value provided by the expanded physical clock. Thus, that value encroaches upon another predefined field of the clock representation. Completion of the instruction is therefore delayed such that the value provided by the expanded physical clock can be accommodated in the clock representation and a correct value for the another predefined field can be provided.

Abstract: A method of operating a computer system is described. The computer system comprises a processor and a co-processor wherein the co-processor is coupled to an output buffer for loading a number of output data units into the output buffer and wherein the processor is coupled to the output buffer for fetching the loaded output data units. The co-processor generates a trigger condition such that the last output data unit is being fetched by the processor from the output buffer as shortly as possible after it has been loaded to the output buffer by the co-processor.

Abstract: A read only storage (ROS) array holds a small set of relatively simple millicode instructions; those millicode instruction routines which are most commonly called on in executing common application workloads. The millicode read only store is implemented as a portion of hardware system area (HSA) storage. The cache control includes a register which contains hardware system area address corresponding to the read only store address. When an instruction fetch request is received by the cache control, the absolute address of the instruction fetch request is compared with the read only store address in the register in parallel with the normal cache directory lookup. If the instruction fetch request matches the read only store address, the fetch is made from the read only store independently of the directory lookup result.

Abstract: A range check instruction sequence, which performs a logical comparison between two 32-bit values and updates the condition code as a result. It operates identically to the ESA/390 instruction compare logical (CLR) except for the way in which the condition code is set. The new condition code is a function of both the comparison result and the previous condition code. If the first operand is greater than the second operand, the condition code remains unchanged. If the first operand is less than or equal to the second operand, the condition code is set to 2 if it was previously 0 or 1, and is set to 3 if it was previously 2 or 3. This may be understood as advancing the state of the condition code among the groups (0,1), 2, and 3 if the first operand is not greater than the second operand.

Abstract: Special millicode instructions accelerate the "inner loop" portion of a millicode routine to execute ESA/390 string instructions. Specifically, these millicode instructions are: Replicate Byte, Find Byte Equal, Find Byte Not Equal, Compare String Bytes instructions.

Abstract: A control store for a microprocessor is divided into two segments with one segment of the control store located on the microprocessor chip and the other segment of the control store located on a separate chip. In multiprocessor applications, a number of the microprocessors share the control store segment on the separate chip. Each control store word includes a field containing a prediction of the address for the next control store word needed by the microprocessor. The predicted address is used to access the control store prior to receipt of the actual request by the processor. When the processor actually requests the next control store word, a compare is performed between the predicted address and the address actually requested by the processor. If they match, the control store word is passed on to the processor. If they do not, the address actually requested by the processor is used to obtain the next control store word.

Abstract: Error detection and recovery is provided in a processor of small size and which can be integrated on a single chip by providing buffers for both data and processor status codes in order to contain errors until a subsequent check point preferably generated at the termination of each instruction is reached without detection of an error. Retry of an instruction can therefore be initiated using the status and data validated at the termination of the previous check point and without placing error correction processing in any critical path of the processor. Error detection is accomplished by comparing outputs of at least a pair of unchecked processors for both memory access requests and output data and status codes. Input to the processors is subjected to a parity check and parity check bits are generated for memory access requests. Error correcting codes are generated for data and status codes to allow correction of single bit errors during transmission within the processor or at a storage system.

Abstract: An instruction processing system and method which utilizes instruction completion to isolate errors, including those in the post-completion processing of operand stores, to an interval between checkpoints, while allowing the processing of checkpointing instructions to be overlapped with that of other instructions. Checkpoints are established before and after such instructions, and all processing (including that of operand stores) from before a checkpoint must be done prior to allowing instruction completion to move beyond the checkpoint. Nevertheless, instructions from beyond a checkpoint are allowed to be processed up to the point of completion while waiting for the checkpoint to be cleared. The point at which instructions must wait on a prior checkpoint is thus moved to the final phase of instruction processing (instruction completion), at significant performance advantage over a conventional implementation in which this waiting is done at instruction fetch, decode, or execution time.

Abstract: An instruction processing system and method which utilizes instruction completion to isolate errors, including those in the post-completion processing of operand stores, to an interval between checkpoints, while allowing the processing of checkpointing instructions to be overlapped with that of other instructions. Checkpoints are established before and after such instructions, and all processing (including that of operand stores) from before a checkpoint must be done prior to allowing instruction completion to move beyond the checkpoint. Nevertheless, instructions from beyond a checkpoint are allowed to be processed up to the point of completion while waiting for the checkpoint to be cleared. The point at which instructions must wait on a prior checkpoint is thus moved to the final phase of instruction processing (instruction completion), at significant performance advantage over a conventional implementation in which this waiting is done at instruction fetch, decode, or execution time.

Abstract: Enables an I/O channel program to use IDAWs (indirect data address words) to control data transfers from/to an I/O (input/output) device to/from either or both of ES (expanded storage) and/or system MS (main storage), in which data moved to/from ES does not move through MS. ES and MS are plural electronic storage media in a data processing system, and the I/O device is any I/O device selectable by the system. Intermixing of data transfers between ES and MS may be controlled by a single IDAW list accessed by a channel control word (CCW) in a channel program in a data transfer direction indicated in the CCW without any channel mode change.

Abstract: Enables a host (hypervisor) to access any location in any guest zone in a large memory, when host and guest operands have small addresses that cannot access locations outside of their own zones. System hardware/microcode provides a particular number of windows for host use. Each CPU in the system has one or more window access registers (WARs), and one or more window registers (WRs). The host uses a load WAR instruction to designate each page frame (PF) in the host zone to be used as a host window, and each PF is associated with a respective window number. When the host receives an interception signal requiring the host to access a guest location represented by a guest zone identifier and a guest small address, the host designates one of its window numbers for an access to this guest location.

Abstract: A system and method for modifying program status words (PSW) with overlap enabled. According to the present invention, an instruction which modifies a PSW system mask, access key, or address space code is executed with overlap enabled. This instruction generates a new PSW. The new PSW is pushed into a queue. Once the instruction is complete, the new PSW becomes an architected PSW. If the instruction does not complete, then the new PSW is discarded. Once the new PSW is pushed into the queue, subsequent instructions may execute using the new PSW. Thus, instructions which modify the PSW system mask, access key, and address space code may execute with overlap enabled.

Abstract: Method and apparatus for correctly predicting an outcome of a branch instruction in a system of the type that includes a Branch History Table (BHT) and branch instructions that implement non-explicit subroutine calls and returns. Entries in the BHT have two additional stage fields including a CALL field to indicate that the branch entry corresponds to a branch that may implement a subroutine call and a PSEUDO field. The PSEUDO field represents linkage information and creates a link between a subroutine entry and a subroutine return. A target address of a successful branch instruction is used to search the BHT. The branch is known to be a subroutine return if a target quadword contains an entry prior to a target halfword that has the CALL field set. The entry with the CALL bit set is thus known to be the corresponding subroutine call, and the entry point to the subroutine is given by the target address stored within the entry.