by M. J. Mack, W. M. Sauer, S. B. Swaney, B. G. Mealey
This paper describes the state-of-the art reliability features of the IBM POWER6™ microprocessor. The POWER6 microprocessor includes a high degree of detection of soft and hard errors in both dataflow and control logic, as well as a feature—instruction retry recovery (IRR)—usually available only on mainframe systems. IRR provides full hardware error recovery of those registers that are defined by the instruction set architecture. This is accomplished by taking a checkpoint of the defined state for both of the core threads and recovering the machine state back to a known good point. To allow changing memory accessibility without using different page table entries, the POWER6 microprocessor implements virtual page class keys, a new architectural extension that enables the OS (operating system) to manage eight classes of memory with efficiently modifiable access authority for each class. With this feature, malfunctioning kernel extensions can be prevented from destroying OS data that may, in turn, bring an OS down.