Modular design techniques improve methods of error detection, diagnosis, and recovery. Theoretical computer (MARCS (Modular Architecture for Reliable Computer Systems)) study deals with postulated and modeled technology indigenous to 1975-1980. Study developments are discussed

Bouricius, W. G.

Cater, W. C.

Jessep, D. C.

Mccarthy, C. E.

Milligan, F. G.

Wadia, A. B.

English

NASA Technical Reports Server

May 1972	 CORRECTED COPY
	 B72-10109 
.
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Techniques for Improving Reliability of Computers 
S 
S
The problem: 
Future computer requirements indicate the need for 
an increase in reliability by a factor of at least 10. These 
improvements cannot result in an undue increase of 
power dissipation, processing time, or the time required 
for system recovery from a malfunction. 
The solution: 
Modular design techniques result in the enhancement 
of computer reliability by improving methods of error 
detection, diagnosis, and recovery. 
How it's done: 
A theoretical computer, MARCS (Modular Archi-
tecture for Reliable Computer Systems), was designed 
with the following objectives: 
A modular system organization for easier error detec-
tion, diagnosis, self-repair, and a significantly lower 
level of redundancy. 
Error monitoring and detection by hardware at the 
module level. 
Distinction between transient and permanent failures 
and catastrophic and non-catastrophic failures. 
System-aided recovery and reconfiguration for opti-
mizing system effectiveness after error detection. 
Program detection and isolation of aberrant hard-
ware. 
The study deals with a postulated and modeled tech-
nology indigenous to 1975-1980. Correction schemes 
fundamental to a modular structure are considered 
which include Triple Modular Redundancy, Quadding 
and Sparing. The organization factor of reliable machine 
design is characterized as logic-based through the archi-
tectural structure of the machine and the fashion in 
which hardware error detection and correction is in-
corporated into the structure by the design techniques. 
The aspect of algorithms used in interactive design by the 
basic processes of recovery and diagnosis are defined and
examined for error detection hardware and system 
organization. 
Several important developments have arisen from the 
MARCS study. They include: 
1) The use of Morphic Boolean Functions. 
2) The new form of Boolean Difference. 
3) Diagnosis procedures prescribable by the RC\'Y 
(Recovery - an interactive programming language) 
Program. 
4) Self-testable implementations of Hamming SEC/ 
DED (Single Error Correcting/Double Error Detect-
ing) encoding and decoding circuitry. 
5) A basic design of the Configuration assignment 
unit module. 
6) Input/Output Processor specification and design 
using error detecting shift register control units. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&PS-TU 
Marshall Space Flight Center, Alabama 35812 
Patent status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
Patent Counsel 
Marshall Space Flight Center 
Code A&PS-PAT 
Marshall Space Flight Center, Alabama 35812 
Source:	 W. C. Carter, C. E. McCarthy, D. C. Jessep 
A. B. Wadia, F. G. Milligan, and 
W. G. Bouricius of 
IBM Space Systems Center 
under contract to 
Marshall Space Flight Center 
(MFS.2 1326) 
Category 02 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
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Techniques for improving reliability of computers

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