Final answer:
A miscompare is shown on the PFD through alert messages or colored flags on key readouts, while the EICAS displays specific system warning messages and possibly an aural alert.
Step-by-step explanation:
A miscompare between the Primary Flight Display (PFD) and the Engine Indicating and Crew Alerting System (EICAS) in an aircraft is indicated differently due to the distinct purposes of these two systems. On the PFD, which primarily displays flight information, a miscompare might be indicated with alert messages or colored indications (often amber or red) on attitude, altitude, airspeed, etc. Conversely, the EICAS, which presents engine performance and aircraft system status, would likely indicate a miscompare with specific system warning messages and possibly an aural alert.
In the case of the PFD, a miscompare might result in a 'flag' appearing on the artificial horizon or an 'X' over an airspeed or altitude readout, along with an appropriate alert message. The EICAS, being centered around engine and systems performance, would present a miscompare through textual and graphical warnings, such as 'ENG 1 FAIL' for an engine discrepancy or 'HYD QTY LOW' for a hydraulic system miscompare, coupled with the illumination of a master caution or master warning light.