AFFORDABLE PORTABLE: If portable computer prices keep...

AFFORDABLE PORTABLE: If portable computer prices keep dropping, they may soon be cheap enough for almost anyone to slip into a briefcase. With price cuts announced Monday by Irvine-based AST Research (D1), for example, its Research Premium Exec 386sx/25 with an 80-megabyte hard disk drive costs $1,895. . . . . That’s a whooping $2,900 drop in price since the seven-pound machine was introduced at $4,795 in September, 1991.