NFG Games + GameSX

The 040EXCEL is a 68040 CPU accelerator board for the XVI/Super series and was manufactured by Makio Suzu. All signs point to it being a doujin effort and not a wide release. It has a 68040 33 mhz as stock, but with some bios/PLD/regulator changes, it can be upgraded to a 68060 CPU. The board also has a slot for SDRAM and up to 256MB can be inserted into the slot. The first 12MB will fill the 68000's regular memory, while the remainder will go to the high memory address.

http://www.gamesx.com/wiki/doku.php?id=x68000:040excel_necessary_modifications

*The Excel uses a modified Jupiter driver that the creator of the Jupiter driver made. First you have to patch the SRAM with the included SRAMPATCH.x in 68000 mode, restart, turn on 68040 mode by flipping the switch you made and then include the Jdash.sys file in your start up config.sys.