Diagnostic system for a digital computer

Details Diagnostic system for a digital computer Diagnostic system for a digital computer

G - Physics

06

F

354/224, 354/225

G06F 11/00 (2006.01) G06F 11/267 (2006.01) G11C 29/00 (2006.01)

Patent

CA 1233256

ABSTRACT OF THE DISCLOSURE A diagnostic system for testing the video output and secondary storage facilities of a computer system. The refresh memory of the video subsystem is loaded with the codes of a character string including the complete set of display characters and the code for a character that is not displayable. A character generator responds to this non-display character with the cyclic redundancy check (CRC) code for the bits emitted by the generator in response to the string of display characters used in the diagnostic routine. A slowed-down replica of video output from the character generator is fed as a stream of bits to a slow speed serial communications port and then to the processor. The processor generates the CRC code in response to the stream of bits from the character generator and it compares this generated code with the CRC code received from the character generator. Similarly, for testing the secondary storage subsystem, certain predetermined data is stored in a portion of a primary memory unit. This data, simulating an MFM-encoded recording of known information, is transmitted by the central processor to the control unit for the secondary storage system, and is looped back through the controller for data separation and decoding and is then returned to the central processor. The returned signal is compared with the unencoded form of the data provided to the controller.

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