Inserted my new 64GB SanDisk UHS-I card into my XPERIA X10i.
ROM: GB 2.3.3 (reduced to 95 system applications)
Kernel: DoomKernel V6 operationally clocked at 1113MHz
Features: XPERIA S applications and Home Launcher
Data Partition: Linked via Link2SD
SDcard: 64GB SanDisk Ultra® microSDXC™ UHS-I
Battery: 1800mAh Mugen Power Battery
Tested the original 64GB exFAT card prior to FAT32 format on my Win7 PC using CrystalDiskMark, HDTune and ATTO benchmark and all returned around 10-13MB sequential write and around 18MB read (Max threshold of my card reader not known)
Formatted the SanDisk 64GB card to FAT32 and 32K cluster size and re-tested the benchmarks with the same results.
Created a second primary 1GB partition formatted as ext3(cause for some result my X10i doesn't like ext4 at the moment)
Used my NAS to copy over my Link2SD partition data from my old 32GB SanDisk UHS-I card, inserted the card and rebooted the phone.
Everything can be seen OK with all applications accessible.
I did mount the card prior to adding the second partition and it showed ~59GB available data in setting->storage. This was what was shown in Win7 both as exFAT and FAT32. The raw SDcard size is seen as ~63GB.
Most Android SDcard benchmark applications show a write speed of 6-8MB and a read speed of up to 18MB. There are constraints on the 64GB card due to the size of the data structure regarding access speed using FAT32.
Other than all the above voodoo there is no real difference to the phone other than the fact I now have 58GB of available disk space.
I could place some of my 720p Video and .flac Music library on the card to see how it goes above 32GB, but I thought I'd run it with just a minimal amount of data on it to see how it goes over a week or two.
The funny thing is that with BSPlayer (video player) and Neutron Music player I can(and do) stream all my videos and music from my NAS with only a few music albums of the week on my phone.
Samba FileSharing App. provides great SDcard access over WiFi AP or WiFi hotspot for low-speed 64GB '
mobile file server' access on the go.
AnTuTu benchmark returns the following disk access results, which are optimistically higher than any other SDcard benchmark.