Toshiba Satellite U300 Series Maintenance Manual page 137

NOTE: The following screen does not display correctly. It will be
amended in the next version.
Press [Enter] Key
Press Enter to execute the VRAM mapping test which displays a vertical line
at four dot intervals using Mode 12.
Press [Enter] Key
Press Enter to display VRAM mapping test using the all dots Mode.
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Satellite U300 and Satellite Pro U300 Tests and Diagnostics Manual
Test Program for Field.