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I am just asking, whether it's technically possible for a SD card to be SD XC, but have SD-HC or SD-NC (normal capacity) capacities, which are well below 64GB.
Of course; in reality, there is no reason for a higher SD card standard to have less storage.
neverMind9
Posted 2018-02-19T08:26:02.253
Reputation: 617
13
There are three separate things conflated here:
The SD/SDHC/SDXC label is marketing that simplifies the above. The main differences are:
In other words the hardware/firmware is the same for SDHC and SDXC, it's just the pre-written data that's different.
Now, there's no reason you couldn't fit a 2GiB flash chip to a SDHC controller, format it as exFAT and call it SDXC. You lose the ubiquity of FAT (users of exFAT have to pay a patent fee to Microsoft, hence it isn't so common) but the extra features of exFAT may make up for it. The SD Association might complain about confusing marketing if you tried to sell it, though.
That said, the formatting of the card is just a case of the data written to it in the factory. If you reformat a 2GB SD card to exFAT you achieve almost the same effect. Arguably it's better since it will work in some old card readers and such whose firmware doesn't support the SDHC protocol.
user1908704
Posted 2018-02-19T08:26:02.253
Reputation: 270
5SDHC and SDXC being the same at the protocol level is a fascinating claim that I see made explicit here for the first time. It is however consistent with my experience (use of cards larger than 32GB in devices that use non-Microsoft filesystems yet do not claim SDXC compliance, such as Raspberry Pi computers), so I should have guessed. – dhag – 2018-02-19T15:09:26.743
1Interesting; my Sony camera demands SDXC for full-bitrate video, yet I don't want to waste 64 GB on it. I have fast (U3) 16 GB cards, yet it rejects them. I shall try to format them in exFAT and see if it fools the camera. But something tells me that, as usual, Sony is more... sneaky. – Zeus – 2018-02-20T05:52:40.840
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The SD association states that an SDXC card has more than 32GB capacity on their website: SDcard.org
This seems to indicate that a smaller card isn't an SDXC card. Of course, the change from SD to SDHC and then to SDXC wasn't only about increasing the capacity.
For example, each new version also introduced faster transfer modes and even within SDHC and SDXC there are multiple upgrades to the standard. The interesting thing is that often these upgrades were also applied to the previous capacity standard. For example, adding the UHS (ultra high speed) bus was done for both SDXC and SDHC cards: Wikipedia on SDXC
AdmiralFreebee
Posted 2018-02-19T08:26:02.253
Reputation: 536
1SD-HC also can have 32 GB but at maximum. – neverMind9 – 2018-02-19T09:30:18.540
1Of course there could be a reason: speed and reliability. Nobody would pay for it probably though. – PlasmaHH – 2018-02-19T10:29:40.593
1@AlexanderKosubek: Do cards that big exist? I'm not even sure I've seen SSDs that big... – user541686 – 2018-02-19T22:54:29.123
1@Mehrdad The largest SD card I was able to find was a 512 GB card, so we're getting there. 2 TB, and even 4 TB SSDs definitely exist. – jrh – 2018-02-20T03:12:48.523
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@jrh: The weird thing is there's been news of this beast since 2009.
– user541686 – 2018-02-20T03:57:52.003Some fake SDs already pretend 2 TB. – neverMind9 – 2018-02-20T07:45:35.417
1
@Mehrdad I don't know if they exist, but they are specified like this. Sandisk tells us, that the "SDA 3.0"-spec based SDXC has from 64 GB to 2 TB capacity.
– I'm with Monica – 2018-02-20T09:58:27.9572My first comment, asking if theTechLord had "2 GB" confused with "2 TB" was based on a misunderstanding: I didn't initially realize, that the question was about if a newer standard card could have a lower capacity and still be compliant to the newer specs. - So, my apologies! - I posted a new comment to clarify on @Mehrdad's f-up, though. – I'm with Monica – 2018-02-20T10:03:54.550
@AlexanderKosubek I should have said 1 GB pr 4 GB instead. Or 256MB. 2GB was just a sample size. – neverMind9 – 2018-02-21T14:06:54.860
I just re-inforced the clarification. – neverMind9 – 2018-02-21T14:09:15.123