As explained in this blog post and accompanying video, each microSD card has a built-in CPU. The CPU of a given make and model number can change at any time and there will be no notice. The manufacturers do not reveal when such changes are made and the microSD card name and model numbers stay the same.
On Hacking MicroSD Cards « bunnie's blog
This means that the same exact card is often not the same card at all. If you have trouble with a card, returning it for replacement with a card of the same model number could resolve the issue.
For instance, the Sandisk Ultra 64 is very popular among T100 users. Some have no issues at all with that card, others have tremendous issues. There seems to be no easy way to identify which sub version of a card one has. Trial and error is the only solution for now.
Last edited by Banise; 01-17-2014 at 10:09 AM.
To complicate things further, even if we DID know what controller was in use on the micro SD card, it doesn't mean similar cards are exactly the same. I used to have a couple of identical motherboards, running the exact same BIOS, RAM, CPU, EVERYTHING exactly the same between the two systems. One had a base clock (they were Sandy Bridge based systems) that was being driven at 100.03Mhz, the other one was driving at 100.17Mhz. What should have been identical hardware (it was all even bought at the sametime, so it should have been the same CPU steppings, etc, etc), was not operating at exactly the same exact speeds.
Since this appears to be a clock speed issue with NCRC, it really might just be that if the micro SD card controller drives the interface at just a few kilohertz off one way or another, it might just be enough to drive it in to the range where the Bay Trail SD host controller cannot cope, and fails to initialize the card.
I think the only two real pieces of advice are
1) Wait and hope Asus can and will release a BIOS fix or driver fix that will correct the problem.
2) Possibly have to try returning your micro SD card and trying a different one
Number 2 could be potentially very frustrating (and possibly cost you some money and deffinitely time) and it could be you strike out with 2 or 3 cards before you get a working one.
It is always possible to it is something wrong with the micro SD card reader itself after all that, in your specific T100.
Sadly, there just don't seem to be any other options right now.
Last edited by azazel1024; 01-17-2014 at 12:58 PM.
I had just gone to the Sandisk site and used their card compatibility feature. The T100 isn't even listed there. Not only that, but I searched other brands online for a non-UHS I class micro SD card (class 10 is good enough for me) and it is almost impossible to find one. This is not to say that these cannot be found. I am getting the impression that all the micro SD manufacturers are going the UHS route, already rendering my new 32 GB T100 obsolete. Even using UHS-I class via a USB 3.0 adapter seems a matter of luck due to the clocking issue. I am new to the tablet world, so it makes me nervous that a feature is already compromised[/B].
Though the embedded card reader is slower than the USB, I thought I could have recovery or alternatives sitting on the card instead of being dependent on always having a dedicated jump drive to carry around. I am not so sure that "ghosting" for full system restore is possible with SkyDrive, and there are no guarantees that internet will be available just when you need to recover, let alone rising data downloading charges. I guess I have yet to determine the T100's best use under its limits.
I am going to research best use of micro SD cards.Believe me, I was not expecting it to perform like a full-throttle laptop but, unless someone more experienced can enlighten me otherwise, this thing may be going back within 6 days (before the 30 days are up). I am crossing my fingers but not holding my breath. In the meantime, I am grateful to you for your commendable research and team work. This is a great site!
Last edited by Carlotta; 01-18-2014 at 10:17 PM. Reason: I had to think it through more.
How about taking the 32 back and getting the 64GB one?
OWNER OF ASUS 64GB T100TA w/128GB microSD, and now running Windows 10
Wanted to give an update on my sdcard issues. My first sandisk 64 GB sdcard wouldn't work at all. Lots of error messages and would stop being recognized by the device after ten minutes. However it did work fine in other windows laptops. Returned the card for a new one and haven't had one problem in two days. S/N is SDSDQU-064G-AC46A.
What am I missing? Was this just for the sake of transitioning people with non UHS-I cards to either a dongled or cloud existence at that price point, then?
It is a big disappointment for me as an introduction to ASUS. I mean, it was supposed to be the newest in its category. In case anyone is wondering, this was a gift. I had been holding out on purchasing anything until I learned more about non-PC/ laptop existence.
So, enuff whining from me then. If an embedded card reader that can handle UHS-I is important to me, I will just have to exchange it quickly.
Last edited by Carlotta; 01-20-2014 at 10:43 AM.
It is disappointing, but it sounds like Asus is aware of the problem and there may be a possible driver or BIOS work around in the works.
For compatibility listing, SanDisk and others aren't going to test and keep track of the dozens to hundreds of new devices a month that are relaxed world wide, especially not in a timely fashion.
Last edited by azazel1024; 01-27-2014 at 08:10 AM.