3 Chun Hok Ho Wayne Luk Jakub M. Szefer Ruby B. Lee 2009 Proceedings of the 22nd IEEE International SOC Conference Sept. 9-11, 2009 This paper describes four techniques for tuning instruction customisation for reconfigurable SoC devices. The proposed approach has been used in deriving custom instructions for advanced bit manipulation applications for the Xilinx MicroBlaze processor. We show that for a transfer coding application, a custom instruction with an increase of 13% in area can result in performance improvement of over 33 times.