X0202 4 2006-09-21 0 0001065246 HI/FN INC HIFN 0001044321 MARXE AUSTIN W & GREENHOUSE DAVID M C/O SPECIAL SITUATIONS FUNDS 527 MADISON AVENUE, SUITE 2600 NEW YORK NY 10022 0 0 1 0 Common Stock 2006-09-21 4 P 0 2680 4.5713 A 1780140 I By Limited Partnerships This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, L.P. (QP), Special Situations Cayman Fund, L.P. (Cayman), Special Situations Technology Fund, L.P. (Tech) and Special Situations Technology II, L.P. (Tech II), respectively. 530,472 shares of Common Stock are held by QP, 144,188 shares of Common Stock are held by Cayman, 112,700 shares of Common Stock are held by Tech and 992,780 shares of Common Stock are held by Tech II. The interest of Marxe and Greenhouse in the shares of Common Stock owned by QP, Cayman, Tech, and Tech II is limited to the extent of his pecuniary interest. Austin W. Marxe 2006-09-25 David M. Greenhouse 2006-09-25