Same here, I look for a very fast MicroSD, in my case is this one " GS-2IN1633X-MLC-32GBX5-B " and no face any issue with the FW5 with my Pokemon Crystal version, the clock works just perfect. For that Pokemon Prism I use mGBA in my PC, otherwise I need to get a everdrive GBC flashcard with isolated Real time clock insteadUpdated 3 ez-junior to FW5 without any problem. Micro SD was a Kingston Class 10.