Abstract: A fault tolerant computer system is provided which includes a first system module with a first processor and a first processor bus and a first I/O bus; a second system module with a second processor and a second processor bus and a second I/O bus; a third system module with a third processor and a third processor bus and a third I/O bus; wherein the first system module further includes a first control device which coordinates transfer of first transaction information between the first processor bus and each of the first I/O bus or the second I/O bus or the third I/O bus; and wherein the first system module includes first comparison logic which compares first transaction information with corresponding second transaction information; wherein the second system module further includes a second control device which coordinates transfer of second transaction information between the second processor bus and each of the first I/O bus or the second I/O bus or the third I/O bus; and wherein the second system module inc

Abstract: A fault tolerant computer system is provided which includes a first system module with a first processor and a first processor bus and a first I/O bus; a second system module with a second processor and a second processor bus and a second I/O bus; a third system module with a third processor and a third processor bus and a third I/O bus; wherein the first system module further includes a first control device which coordinates transfer of first transaction information between the first processor bus and each of the first I/O bus or the second I/O bus or the third I/O bus; and wherein the first system module includes first comparison logic which compares first transaction information with corresponding second transaction information; wherein the second system module further includes a second control device which coordinates transfer of second transaction information between the second processor bus and each of the first I/O bus or the second I/O bus or the third I/O bus; and wherein the second system module inc

Abstract: The present invention is a two beam, double pass, phase shifting interferometric system for characterizing the phase profile of a radiation path. In the preferred form of the invention, a monochromatic beam is split into a reference beam and a test path beam. The test path beam is directed toward a fixed reflector which in turn directs that beam to the image sensor with a fixed length in the direction of propagation. The reference beam is directed to a movable reflector which directs that beam also to the image sensor, while introducing phase modulation. The system provides a measure of phase offset introduced into the reference beam at times of minimum or maximum intensity as measured by each photo detector in the image sensor, as the phase modulation of the reference beam is stepped over one complete wavelength.