Lumia 640: Which Micro SD Card should I use?

[Windows Central Question]

Hey guys,

I got a Lumia 640, and the selller sold med a Sandisk 16 GB 80 MB/Sec card. I haven't opened the card yet, and I am not sure if I should do it either. I've read somewhere that the phone only can do up to 25 mb/s on the micro sd card. Is this true?

If it is, then I should go for a bigger card with around 25/30 mb/s and get more capacity instead right?

Is there no Lumia that takes over 25 mb/s micro sd cards?

 

[Nicholas Ek]

Uhh, B/b is a very important distinction, you know?
Class 10 cards offer performances starting from 80 Mb/s, which in B terms would be 10 MB/s.
Lumias do support Class 10 cards.

 

[MikeJezZ]

Hey, I am OP btw

I bought this Sandisk 16GB Ultra Micro SD (SDHC) Card 80MB/s UHS-I Class 10 with Adapter , which has 80 mb/s transfer. But I've read the phone can only take up to 25 mb/s ?

Form Factor microSDHC, microSDXC
Available Capacities 8GB, 16GB, 32GB, 64GB, 128GB
Performance/Speed 8GB: Up to 48MB/s read speed, write speed lower
16GB-128GB: Up to 80MB/s read speed; write speed lower.

 

[Nicholas Ek]

As I said, capitalization is important.

Either way, the device's inner transfer speeds are higher than the SD card's, and since it specifically supports Class 10 as well, I see no problems with using the card you bought. Where did you read the 25 thing?

 

[MikeJezZ]

windowscentral.com/which-microsd-cards-work-microsoft-lumia-640

 

[MikeJezZ]

Here on this forum. I can't post link yet so can only quote:

"It will work with SDHC and SDXC. The difference between HC and XC is that the size of HC is between >2 and 32 GB and the size of XC is 32 GB to 2TB. (And from 32 onwards you can not use FAT32 formatting). There is no max size for your phone the 128 GB is "just" put in the spec because that is the current max size for microSD cards and SDXC"

"Side note: A class 4 card may not work because it is to slow. UHS (Ultra High Speed bus) standard is not supported so you will not get 30 or 48 MB/s because the max speed of the HIgh Speed bus in your phone is 25 MB/s." - forums Ambassador Harrie-S

 

[Nicholas Ek]

Take a look at https://www.sdcard.org/developers/overview/speed_class/

I looked into documentation that is available for the public for Windows Phones and there is no upper bound limitation mentioned. However, UHS support depends also on the circuitry, which I am guessing Lumia 640 lacks. Base-level UHS (UHS Class 1) is equivalent to regular Class 10 in terms of minimum speed - therefore you can go with a regular Class 10 (non UHS), being cheaper, and still get max performance for your phone.

 

[MikeJezZ]

So there should be no limit in transfer? So I would gain benefit of a 80 mb/sec transfer?

 

[rollindice]

I'm using http://www.amazon.com/gp/product/B00M55C1I2?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00 with no worries

 

[Nicholas Ek]

So there should be no limit in transfer? So I would gain benefit of a 80 mb/sec transfer?

That 80 MB/s is purely theoretical, by the way, i.e. you're not gonna reach it in real life in any device you put the card in. Either way, I just checked the card and it seems overkill in price. Just get a cheaper Class 10 card.

 

[MikeJezZ]

So as long as its a class 10 card, I should just ignore the the speed?

 

[Nicholas Ek]

So as long as its a class 10 card, I should just ignore the the speed?

Class 10 means that there is a minimum performance level of 10 MB/s. Depending on what you plan to use it for, even that could be overkill. However, you can never go wrong with a Class 10, be it UHS or non-UHS. And they can be found for quite cheap these days.