A highly integrated, fault-tolerant minicomputer: the NonStop CLX

Abstract

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.

Vision for cross-layer optimization to address the dual challenges of energy and reliability

“…For example, aeronautic and space systems often run three or more computations in parallel and vote on the result to avoid single or multiple failures [13], [14]. Critical commercial systems run two copies in parallel to detect errors [15], [16]. Distributed systems use redundant servers to balance the load and tolerate both interconnect and node outages, relying on the ability to obtain sufficiently equivalent service from different resources.…”

Design methodology for system correctness: lessons from the Tandem NonStop CLX

“…Besides having a need to be correct (and complete), it needed to avoid hard-coded references to relocatable sections of code or data. Also, as an optimizing feature, the flJ'St lines of each macro-instruction were to reside in a skipping region (see [1]) and do not sequence like normal micro-instructions. Instead of fragmenting the code, source reorganization was chosen as a postprocessing step, relieving firmware designers from this complexity.…”

“…The methodology presented here is based on the design experience of the Tandem NonStop CLX™ CPU [1]. It grew out of planning, on-the-job decisions and lessons learned in retrospect.…”

Built-in-self-test for the Tandem NonStop CLX processor

“…A CLX system can have from 2 to 6 single-board processors. The processor design is based on 4 custom CMOS chips, a 32K x 60 cache/control store static RAM array, and a 4 MB main memory array [1]. An optional expansion memory board of 2, 4, or 8 MB may be added to each processor.…”