128GB micro SDXC is slow and messes up data.

Many sites say that FAT32 is the best format; however, I don’t understand this “4GB limit”. Do they mean you can’t transfer more than 4GB at a time, or do they mean no matter how much memory your card holds, it will hold 4GB instead of 128GB when using FAT32?

Right now, the default format is exFAT, but it’s as slow as heck and has some errors transferring files from PC to card. I also tried NTFS and it’s equally slow.

This leads to a question: how the heck can I transfer a bunch of data quickly without having any problems? The card I purchased was the older version of the card from Amazon by a seller and not the newer version of the card straight from Amazon themselves.

:smiley:   Hi Parrothead,

Dear member of SanDisk Community, welcome .


1-     Transfer speeds, do not depend the format.

2-     In Fat32 (it’s an old format, compatible with many devices), the “limit of 4 GB” refers to the “size of a single file”.

3-     For your Sandisk microSDXC of 128GB , is recommended the format, exFAT (is the more modern).

4-     If you think, that the speed is slow, try the following:

4.1-  Put the card in a laptop, directly to the port-card (not a USB card-reader).

4.2-   Then, you can measure the speed with (app portable, free): USB CrystalDisk Mark, http://filecloud.io/9hqxp6fc

4.3-  If still bad: in Start / My Computer, on the card icon, click the right mouse button, and then click in Properties/Tools/Error Checking and Repair.

4.4-   If still bad: try formatting with (free): USB Flash SD Formatter, http://filecloud.io/jqtu1byc

5.0-  If still bad, you can try with these apps portable (free), _ if it’s fake: _

                                                         - USB Flash H2testw,    http://filecloud.io/jl4fhn9b       -It’s the classic utility, but for 64 Gb, it takes ~ 4 hours.

                                                          - USB Flash FakeTest,  http://filecloud.io/n074g3x5    -It’s similar, but has a quick option, and takes minutes.

5.1-   To obtain the internal data of the UFD, you can use (apps portable, free):


                                                - USB Flash ChipGenius,   http://filecloud.io/rqa7etmv
                                                - USB Flash DriveLetter,      http://filecloud.io/vgqzcdyh
                                                - USB Flash Deview,            http://filecloud.io/srp2hegw

Luck, and then you tell us, what happened, please.

Regards, Alfred.                                                             (Google translated)

For some strange reason, exFAT won’t go any higher than 4GB.

:smiley:   Hi,

5.2-  If the above steps have not solved the problem, do not grieve more, contact SanDisk Technical Support who will replace the device, if it’s authentic and is within warranty. Link: http://www.sandisk.com/about-sandisk/contact-us/


Regards, Alfred.                                                             (Google translated)

This just in, that I accidentally purchased fake micro SD cards from 3RD-Party dealers at Amazon.com.

Was it from this seller? cause i just bought one and mine’s only showing 23gb


Also notice the minor bit of miss infomraiton on the. This product is a 633x speed MiniSD card, Class10 XC-1 that runs at max 95mb per second …but only for Read. …for writing it’s a very slow 20mbps. So you’ll spend hours and hours loading it. Hidden info on the back of the package in the top right corner. There are others that are same speed for read & write. This one implies such on the front of the package. Bit of a scam.