What MicroSD card do you have ?

[glx]

I got one of these: http://www.amazon.com/Samsung-Class-Adapter-MB-MG64DA-AM/dp/B00IVPU88U/ref=pd_sim_147_2?ie=UTF8
Works fine, but not as fast as the description says :/.. Read-speed is about 75MB/s, writing about 25MB/s, but I have BitLocker enabled and it's formated in NTFS, maybe there's some potential for tweaking.

 

[sharpuser]

SanDisk 200GB. Works great. Backups set to this drive/disk.

 

[CrippsCorner]

Wow so someone actually bought one

 

[Magic]

Sandisk Ultra SDHC. Runs my Steam games like a champ.

 

[sharpuser]

The 200 GB works perfectly. I get about about 62 MB/sec from the SP3 drive to the micro SDXC, and 14 MB/second transfer from anything in my SP3 USB port to the micro SDXC.

 

[No_ax_to_grind]

The 200 GB works perfectly. I get about about 62 MB/sec from the SP3 drive to the micro SDXC, and 14 MB/second transfer from anything in my SP3 USB port to the micro SDXC.

Never been a big fan of SanDisk. To answer the OP, had a 128GB Patriot mSDXC in my SP3 i5/256/8, i7/512/8 and SP4 i5/512/16; just now upgraded to a Lexar 200GB I got on eBay (just like two of my SPs to-date for the pundit previously in this thread) and so far it's worked flawlessly. And it's FAST.