International Business Machines Corporation

George L Bond

Philip M Ryan

Akella V Satya

Frank P Cartman

The makeup of memory words is controlled by a memory address permutator that permits up to 2.sup.n ! input bit combinations. The particular combinations used in any decoder is dependent on the particular application. The new permutator also permits scattering of certain faults throughout the usable memory address space while simultaneously accumulating other faults in deallocated sections of the memory.

Fault alignment control system and circuits

A fault alignment exclusion method and apparatus is disclosed which operates to prevent the alignment of two or more defective bit storage locations at an address in a memory array. The disclosed memory comprises a plurality (n.times.m) of separate memory chips arranged in a matrix of n rows and m columns. Each of the chips contains a large plurality (64K) of individually addressable bit locations. A plurality of data words, each containing m (72) bit positions are transferred from the memory array to a n (16) word m (72) bit position buffer during a memory read operation. Steering logic responsive to control signals is disposed between the memory and the buffer which permits the n chips in each column of the array to be effectively rearranged selectively within the respective columns so that the relationship of any given chip to a position of the 16 storage positions in a corresponding buffer column may be selectively changed by the control signals applied to the steering logic. The control signals are developed based on defect data stored in an error map such that each memory address contains no more than one defective location.

Multi-bit error scattering arrangement to provide fault tolerant

A memory system is provided with a simple flexible control arrangement for assigning locations in an alternate memory as replacements for previously identified defective fault areas in main memory. The assignment of the replacement locations in the alternate memory is made on a selective basis taking into consideration the defect status of other failure independent bit positions of a data word and the power of the ECC code which is used in connection with the memory system. A relatively small writable index, which is addressed by a subset of the main memory address signals, provides a partial address and control fields to the alternate memory in accordance with control data transferred from the host system. Control data is developed by the host system each time it is powered on and is based on identifying each defective location in main memory through a diagnostic routine and analyzing the defect distribution in a way to provide control signals which minimize the number of replacements that are assigned and maximize the number of data words that can be transferred from the memory system to the host system before an uncorrectable error is encountered by the ECC system.

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Fishkill, NY, United States of America

George L Bond