Abstract: An embodiment of the present invention is a head disk assembly (HDA) simulator that outputs a flexible, totally electronic simulation of an HDA. It outputs a programmable standard HDA signal. As such the HDA simulator generates the head signal that a functioning, already servo-written HDA would provide. This signal can be ideal, eliminating any anomalies and inconsistencies inherent in electromechanical devices. Quantifiable amounts of anomalies can be systematically introduced to allow design margin testing. The HDA simulator is controlled in two ways. First, by allowing a user to choose items from four menus. And second, by allowing the user to use a built-in text editor to edit ASCII files that control the servo patterns and simulator operation. Independent channels of repetitive signals are available to specify sync, servo and data patterns. For any given simulated head position, simulated adjacent tracks are generated and then mixed-in at an appropriate ratio.

Abstract: A microcomputer controlled media and disk testing system having a media servowriting subsystem and a certification subsystem. The servowriting subsystem comprises a precision magnetic read/write (R/W) head positioning device based on a laser positioning device and pattern generating and writing circuitry. The certification subsystem comprises of an apparatus to open bit windows and adjust thresholds and to assess the quality and nature of defects from the positions of bits and their analog characteristics when read back relative to such windows.