Opps I forget the links are kind of hidden, this is copy and pasted from page 1 of this thread.
MC Cthulhu newest firmware: http://www.godlikecontrols.com/download/cthulhu/MCCthulhu23.zip
MC Cthulhu Variations firmwares: http://www.godlikecontrols.com/download/cthulhu/MC_Variations.zip
As of right now v 2.3 is the newest firmware.
For the MC Cthulhu they are part if the flash update, the 10 ms file is only if you have stability issues with the 1ms version.
It is detailed in the read me txt file.
Slightly off topic but I say it just for everyones benefit
Keep in mind the PS3/PC version of the board is not reflashable, only the MC Cthlhu version.
You will need the MC Cthulhu Upgrade Kit $12 to upgrade a Cthulhu to a MC Cthulhu