Abstract: Control logic for controlling references to a cache (24) including a cache directory (62) which is capable of being configured into a plurality of ways, each way including tag and valid-bit storage for associatively searching the directory (62) for cache data-array addresses. A cache-configuration register and control logic (64) splits the cache directory (62) into two logical directories, one directory for controlling requests from a first processor and the other directory for controlling requests from a second processor. A prefetch buffer (63) is provided along with a prefetch control register for splitting the prefetch buffer into two logical channels, a first channel for handling prefetches associated with requests from the first processor, and a second channel for handling prefetches associated with requests from the second processor.

Abstract: In order for any failure of the power supply unit for two read-write memories which are operable in parallel, not to result in irreversible damage to data, two parallel power supply circuits are provided for the operation of the memories. Each power supply circuit is capable of supplying the operating current of one of the memories and the standby current of the remaining memory. Each of the power supply circuits in the power supply is buffered with capacitors in such a manner that, upon a fault in one of the power supply circuits, the output voltage, as soon as the capacitive buffer declines from a normal operating voltage to a threshold voltage and to a minimum operating voltage, data secure current reducing steps are taken.