The NonStop CLX, a highly integrated version of Tandem Computers' fault-tolerant NonStop architecture, is described. An overview of the system block diagram and a detailed description of the CLX processor is given. The processor is based on a custom CMOS chip-set developed using silicon compilation techniques. The CPU micro architecture is a hybrid of traditional minicomputer and high performance microprocessor architectures. This merging leads to a number of novel structures including a single static RAM array that is used as writeable control store, data cache and page table cache. The processor includes a high degree of fault checking in order to assure data integrity and fault-tolerant operation.