I did some tests on 100D, it doesn't accept 240 MHz overclock at all (*both 5D3 and EOSM does for some time @ 240 MHz but not practical), tried with only write benchmark and with *
forcing patch*, no sign of working 240 MHz overclock on 100D.
*on 5D3 240 MHz does work but only for write operations, read operations won't be possible. on EOS M it does work with *forcing patch* but not stable until the card become inaccessible.
BTW, 240 MHz does work on 650D/700D/6D/70D without a problem (with compatible card).
Personally I won't touch UHS stuff again until I get the following:
Xilinx QEMU includes UHS emulation (along with some other nice stuff) and is based on QEMU 2.6.x (at the time of writing). Currently we have patches for QEMU 2.5.0 and 2.9.0, and for the Xilinx version, it will be something in-between. If there is interest, I can commit the patches.
It might be easier to spot the differencees among e.g. 100D and 700D regarding SD configurations using QEMU.