A METHOD AND APPARATUS FOR REDUCING RAM SIZE WHILE MAINTAINING FAST DATA ACCESS

摘要

A method and apparatus for reducing the amount of RAM required while maintaining fast data access. Data records are often saved in nonvolatile memory in order to maintain the contents of the data records even when the circuit is powered down. In the present invention each record in the nonvolatile RAM collection of data records is input to a function H(x) that outputs a tag value. The calculated tag value is saved in predetermined memory locations in RAM. Each calculated tag is shorter in length than the record saved in nonvolatile RAM. Therefore less RAM is required to save one tag value for each data record than is required to save the entire collection of data records in RAM. The value of H(y) is calculated when a data record entry corresponding to y is desired. Then the value of H(y) is compared to all the values in the tag value table. If a match is found, the corresponding record from its location in non-volatile RAM is retrieved and compared to y. If the values do not match the tag value table is searched for another location matching H(y). The result is a very fast comparison with the contents of nonvolatile RAM requiring only a minimal amount of RAM.