Abstract: Data transfer between subsystems of an information handling system employing a multiple subsystem clock environment architecture, or between multiple information handling systems operating with different clock frequencies, is synchronized using a timing aligned multiple frequency synthesizer with a synchronization window decoder. A frequency generation circuit in circuit communication with a data synchronization circuit functions to produce a synchronized timing signal(s) to permit a central processing unit operating in one subsystem clock environment to function with a peripheral subsystem(s), such as a memory controller, operating in a different subsystem clock environment, or permits information handling systems operating with different clock frequencies to function with one another. Data transfer synchronization delays are reduced and mean-time-to-failure of signal synchronization accuracy is increased by eliminating metastability effects from the synchronization circuitry.

Abstract: A logic circuit mechanism for inducing a processing unit to release a LOCK signal that the processing unit uses to secure continuous access to a memory system during read modify write operations requiring "atomic" (continuous) access. The processing unit has an internal cache enabling it to set up consecutive memory access operations at a pace such that the LOCK signal could be held continuously active while a string of atomic memory accesses is carried out. The present circuit mechanism prevents premature release of the processing unit's LOCK signal, by asserting a Hold signal which requires the processing unit to release its LOCK signal but only after that unit has fully completed its current atomic access operation.

Abstract: A personal computer has two memory banks respectively connected to two parity check units operative to detect parity errors. Upon doing so, each unit feeds a parity error signal to a separate latch. The latches are connected to a logic circuit which is in turn connected to an interrupt controller that initiates an interrupt when a parity error occurs. One latch is further connected to a check bit of a register of an I/O port and the check bit is set by the one latch. An interrupt handler reads the register and provides messages indicating which memory bank caused the parity error.