SPring-8 continues its operation over 10 years. Recently, we encounter the need to replace commercial I/O boards due to manufacturing discontinuances. Also, early introduced GPIB control causes instabilities on our control system. In this paper, we report upgrade on these issues for RF control system at SPring-8. For the replacements of I/O boards, we needed some idea for restricted time due to short shutdown period of accelerator operation, and for large number of signals. Therefore, we developed new boards [analog input board (AI) and pulse train generator board (PTG)] for smooth replacements. The new boards were designed to have similar signal cabling scheme and software application with current system. Also, additional improvements (higher signal density, better resolution for AI, flexible logic with logic-reconfigurable VME board for PTG), were introduced at the same time. For AI, ~40 boards were successfully replaced in short time, then we achieved better resolution and reduction in number of boards. For the replacement of GPIB control, we introduced small embedded PC (Armadillo) instead of GPIB-RS-232C converter. Thus, we could improve the stability of the RF control system.