As well as having Microsoft Windows 3.0 installed on the capacious 60Mb hard disk, Tandy Corp’s subsidiary GRiD Systems Inc’s new lap-top dispenses with the irritating mouse, replacing it with an Isopoint tilting bar to control the cursor, installed immediately below the space bar on the keyboard. The new machine, launched yesterday in Boston, also uses the 20MHz version of the 80386SX chip to put it close to the top in terms of laptop performance – but with prices starting at $6,300, the new GRiDcase 1550sx is not cheap. Weighing in at 12 lbs, the machine has 2Mb of memory, 3.5 floppy, the hard disk has 16mS access time and the thing comes with black-on-white liquid crystal diode display with VGA graphics; the battery life is about three hours. Options include 120Mb disk, built-in 2,400 bps modem, and a rechargeable battery; it is planned to be available from next month.