With earnings per share nearly 18% ahead at $1.53 on turnover up 10%, and sales 14.3% up, well ahead of expectations, IBM gave Wall Street a fillip yesterday morning. And while the tax rate was lower than this time last year at 40.6%, it was still two percentage points higher than the figure on which analysts had done their sums. IBM did not this time break out the effect of the sinking dollar in improving its dollar performance. The shares put on $1.625 at $115.25 by New York lunchtime on an otherwise dull morning with the Dow off 11. Details of the figures, pages 4, 5.