+1. Tried a 64GB sd card in Omega2+. I did update the firmware during setup on 5th Jan 2017.
root@Omega-C195:~# dmesg | grep -i mmc -C5
[ 0.601658] 8021q: 802.1Q VLAN Support v1.8
[ 0.610493] mtk-linkit bootstrap: Version :
[ 0.614929] mtk-linkit bootstrap: Revision :
[ 0.627322] VFS: Mounted root (squashfs filesystem) readonly on device 31:5.
[ 0.635412] Freeing unused kernel memory: 156K (803e9000 - 80410000)
[ 1.160220] mmc0: new high speed SDXC card at address 0007
[ 1.166137] mmcblk: probe of mmc0:0007 failed with error -28
[ 1.671539] init: Console is alive
[ 1.675212] init: - watchdog -
[ 4.101087] usbcore: registered new interface driver usbfs
[ 4.106789] usbcore: registered new interface driver hub
[ 4.112332] usbcore: registered new device driver usb
--
[ 55.808837] random: nonblocking pool is initialized
[ 2330.417345] msdc-1 -> cmd<13> card<0> power<2> <- msdc_ops_request() : L<2120> PID<kworker/u2:2><0x2e>
[ 2330.426807] msdc-1 -> cmd<13> card<0> power<2> <- msdc_ops_request() : L<2120> PID<kworker/u2:2><0x2e>
[ 2330.436277] msdc-1 -> cmd<13> card<0> power<2> <- msdc_ops_request() : L<2120> PID<kworker/u2:2><0x2e>
[ 2330.445739] msdc-1 -> cmd<13> card<0> power<2> <- msdc_ops_request() : L<2120> PID<kworker/u2:2><0x2e>
[ 2330.455755] mmc0: card 0007 removed
[ 2614.242498] mmc0: new high speed SDXC card at address 0007
[ 2614.248482] mmcblk: probe of mmc0:0007 failed with error -28