Abstract: In a cache memory unit including a cache directory identifying signal groups stored in an associated cache storage unit, apparatus and method are disclosed for searching the cache directory during a second portion of the cache memory cycle when the cache directory is not needed for normal operation, to determine if an invalid signal group is stored in the associated cache storage. When an invalid signal is found in the cache storage, this signal group is rendered unavailable to the data processing unit during the present cache memory cycle without interrupting the normal cache memory operation during succeeding cache memory cycles.

Abstract: A microprogrammed data processing system includes a cache memory, a decimal unit and an execution unit. The decimal unit receives operands from cache memory, strips the non-decimal digit information from the operands, and assembles the 4-bit decimal digits from the operand into words containing a maximum of 8 decimal digits for transfer to the execution unit. The execution unit processes the words in accordance with a decimal numeric instruction. The throughput of the system is increased when processing short operands which contain 15 decimal digits or less by apparatus in the decimal unit which detects the short operand and determines the number of cache memory cycles between the cycle the first word of the short operand is received from cache memory and the cycle on which the first assembled word is transferred to the execution unit for processing.

Abstract: In a data processing system, groups of characters to be manipulated in a predetermined manner are transferred between storage units and a central processing unit by apparatus and a method which identifies and corrects a character of a group with sign information superimposed on an identified character position for data entering the central processing unit. After identification of the character position containing the sign information superimposed on a character position, the value of the character in the identified character position is determined by apparatus removing the superimposed sign information and such value is placed in such identified character position in the entering character group. A data string including an identified character position can then be entered in the execution unit of the central processing unit for execution of instructions.

Abstract: In a microprogrammed data processing system in which the boundaries of the operands or data strings identified by the descriptors are not constrained to coincide with boundaries of the units of addressable memory space, i.e., words, the time required to retrieve, execute and store operands of a three descriptor instruction, wherein two descriptors define the memory address of the initial operands and the third descriptor defines the memory address of the resulting operand, can be reduced by prefetching the two words which include the boundaries of the operand (data string) identified by the third descriptor. After execution of the instruction, the boundary words of the resulting operand (data string) can have the rewrite data, that is the data of the boundary words which are not part of the resulting operand, and should therefore be retained and inserted in appropriate positions of the appropriate boundary word by a retrieval of the boundary words which do not interrupt the normal data processing sequence.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which, in response to a microword indicating that the result of the decimal numeric calculation is a short operand, that is, a predetermined number of words or less, and in accordance with an instruction descriptor, generates a count of the number of words of the resultant operand the decimal unit will transfer to memory.

Abstract: A cache unit includes a cache store organized into a number of levels to provide a fast access to instructions and data words. Directory circuits, associated with the cache store, contain address information identifying those instructions and data words stored in the cache store. The cache unit has at least one instruction register for storing address and level signals for specifying the location of the next instruction to be fetched and transferred to the processing unit. Replacement circuits are included which, during normal operation, assign cache locations sequentially for replacing old information with new information. The cache unit further includes apparatus operative in response to a first predetermined type of command specifying the fetching of data words to set an indicator flag to a predetermined state.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which is conditioned by the instruction descriptors in advance of receiving the operands to align the decimal digits of the operand words as the words are received by the apparatus from memory.The descriptor information for each operand includes the scale factor, the position of the sign, the position of the most significant character within the word, whether it is a floating point or scaled operand, the number of bits in each decimal character, either 4 or 9 bits, and the length of the operand.The apparatus is conditioned by the descriptor information to align the two operands for processing.

Abstract: In a data processing system wherein memory space in a memory unit is divided into addressable locations capable of storing a group of signals of predetermined number called signal words, and wherein an entire word or groups of entire words are exchanged between the memory unit and a central processing unit, more efficient operation of the data processing unit can be obtained if groups of related signals called operands can be stored consecutively in the addressable locations without regard to the word boundaries. Thus, operand boundaries can have arbitrary positions in boundary words. When a word containing an operand boundary is transferred to the central processing unit, non-operand data is also transferred with the word. The non-operand data occurring in the boundary words is removed from the operand signal group and stored in the central processing unit.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased by apparatus which counts the number of leading zero digits of an operand on the cycle in which the operand word is processed through the decimal unit and sends that count to the execution unit in response to a predetermined microword.The apparatus counts the number of leading zero digits by first storing in a register the number of words the decimal unit will not send for processing as determined by an instruction descriptor. As the operand is received by the decimal unit, most significant word first, the number of leading zero digits in the operand is added to the register on the same cycle the operand word is processed through the decimal unit, thereby generating a count of the number of zero digits in the operand that the decimal unit will send for processing. This leading zero digit count is available to the firmware in response to a microword command.

Abstract: In a microprogrammed data processing system the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which indicates to the microprogram the characteristics of the operand being processed. This enables the proper microprogram subroutine; that is, if the operand is a floating point or a scaled number, has 4-bit decimal digits or 9-bit decimal digits, has an overpunched leading sign or trailing sign, has an adjusted length less than or equal to 63 decimal digits, whether the operand is a long or short operand, and whether the resulting operand is equal to zero or has an overflow.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which receives a long operand, greater than a predetermined number of words, which is the result of the calculation, assembles the resultant operand in accordance with an instruction descriptor, and transfers the resultant operand to memory.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased by apparatus which counts the number of effective digits in an operand which is the result of a decimal numeric instruction being processed by the system. The apparatus receives operand words the operand's least significant word first, in response to a predetermined microword.The apparatus includes a first register which stores a count of one less than the number of words received; an adder which increments the output of the first register if the word received has a decimal zero in the high order position of the word; and a second register which stores the output of the adder in a word count portion and the number of leading zeros in a digit count portion of the second register. The second register is loaded on the same cycle the word is processed providing the word does not contain all decimal zeros.

Abstract: In a microprogrammed data processing system the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which strips zone bits, sign, exponent and non-operand characters from the operand when the operand is received from memory and appends the zone bits, sign, exponent and non-operand characters to the resultant operand when stored into memory. The control signals for stripping and appending information is enabled by shifter logical elements.