Talk:SD card

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X Speed Ratings: SLC vs MLC,?

Propably, a thing related to speed ratings of SD cards is the SLC vs MLC issue. Although it is almost never mentioned by SD cards distributors, it seems the critical factor impacting access times, write and read speed, as well as the media durability. I'm absolutely not any kind of expert here, I just wanted to give a hint, hoping it's usefull for soemone more knowledgable. I can't say what is the link between 60, 133, 150x etc. ratings and the SLC/MLC, but there is something on here it seems. Or are the MLC not present on the market anymore?

Searching for "slc mlc sd" gives eg. this document: The Samsung SLC NAND Flash Advantage.

Compatibility section

I think there should be a separate section on compatibility, e.g. between SD and MMC cards, the issue with 2GB and larger SD cards, etc.

Use of SPI mode withput a license

It is stated repeatedly throughout the article that host controllers can access SD cards through the SPI mode without needing to obtain a license. I am curious if there is any reputable source we can supply, which confirms that the SD Organization actually permits royalty-free use of their intellectual property with respect to hosts accessing SD cards via SPI.

I am aware that the simplified specification is supplied without requiring developers to sign a license agreement, and I am also aware that various reverse-engineering efforts succeeded in determining most of the SPI command set even before the simplified specification was released. However, if you visit the SD Association's web page, they clearly state that their decision to publish the simplified specification does not constitute a grant of any license to implement patented methods described by the specification. Reverse-engineering has never conveyed permission to implement patented methods.

If the SD Association really has made a promise to permit royalty-free host implementations over SPI, then it would be very useful to provide a link to confirm this fact.24.222.2.222 (talk) 12:57, 27 November 2014 (UTC)

I contacted SD Association a couple years ago and the person said that I didn't need a license to create a product that interfaced to SD card slots using SPI-bus. I think primarily because SPI-bus is kind of an "open bus". I seem to remember asking for the same proof, but I can't remember if there was any, anyway I haven't spent any time digging through their site to see if their ever clarified it. • Sbmeirow • Talk • 21:46, 28 November 2014 (UTC)

If you want to make and sell an SD card, then you need a license. If you want to add SD-bus capability to an IC chip so it can communicate with an SD card, then I think you need a license. If you want to use their symbol, I think you need a license. I'm not a lawyer, nor a SD Association representative, so you should contact them for accurate answers for specific license questions. • Sbmeirow • Talk • 21:46, 28 November 2014 (UTC)

I am not a lawyer nor an expert, but it strikes me that SPI is the prior art and SD cards were designed to be backward-compatible with it. Serial Peripheral Interface Bus says this is a de facto standard with no established publication defining it. (Section 5 of that article says that implementations vary widely.) This suggests that the SD Association does not even own this interface mode, in which case it might not be prepared to "promise to permit royalty-free" use of it. Spike-from-NH (talk) 23:48, 28 November 2014 (UTC)

versus eMMC and SSD

How would these be ranked in terms of best and worst? Would it be SSD (solid state drive) > SD card (secure digital) > eMMC (embedded MultiMedia card/controller) or some other order? Is SD better than HDD (hard disk drive)? Is eMMC better than HDD? --64.228.88.135 (talk) 00:16, 1 December 2014 (UTC)

What's better, train or bicycle? It depends on the criteria (f.e. purpose, usability, compatibility, size, speed, capacity, age, reliability, costs) used for the comparison. They cannot reasonably be compared except for in a particular context of application. --Matthiaspaul (talk) 16:27, 14 January 2015 (UTC)

Another point is that SD cards use for storage the same technology as SSDs, that is Flash memory. The main difference is that the interfaces are different. Interfaces are usually classed by speed, as this is the main factor. In the case of UHS-II it is 312 MB/s[1], while with SATA-3.2 it is 2GB/s[2]. So SATA is capable of the faster access, but of course these figures are in practice a lot lower, as flash memory is usually slower than either of these figures.

Traditional hard drives are usually slower than flash memory, but of course this won't always be the case, it depends very much on the technology used. And MMC technology is outdated[3], and a lot slower than SD or SATA.

So it is MMC < SD < SATA, if you look at peak performance from the latest standards. And usually HDD < flash memory, but this won't always be the case. Note that MMC and SD are always flash memory (I think) and SATA drives can be flash memory or hard disks. --Mrjulesd (talk) 17:25, 14 January 2015 (UTC)

"A SD"

Sdxu has just globally changed "An SD" (pronounced "an ess dee," I think) to "A SD" (pronounced "a SecureDigital"? I think not), change summary "corrected grammars." I've reverted; I brought up this question, without response, so long ago it's now archived. If there is a policy on this, I don't insist; but after Sdxu's change, it just looks wrong. Spike-from-NH (talk) 14:23, 14 January 2015 (UTC)

The rule to append an "n" to the indefinite article "a" is based on how the first letter of the immediately following word is pronounced, not how it is spelled. If the sound starts with a vowel, an "n" is added, otherwise not. Therefore, "an SD card" is correct. As English pronunciation can differ in different parts of world, this can sometimes cause confusion, but AFAI see it should not in this particular case. --Matthiaspaul (talk) 16:15, 14 January 2015 (UTC)

Oh, Matthiaspaul is right, I did think about it awhile before editing, but I bear the word "secure" when thinking a or an, but not "s", which apparently "secure" got no vowel at the front. It's about the "reading practice": when reading some acronyms which apparently have pronunciation, it goes, but when there is no, I return back to the long form, especially only a few or 2 letters. I check back Oxford Advanced Learner's Dictionary (British's), it's as Matthiaspaul said, follows how the first letter is said, but then the 2nd question comes: article a got 2 pronunciation forms: "normal" or strong form, what Spick-from-NH talks about is the strong form. I think it's ok to have a or an, but make it ALL a or an. It's not good to have a and an at the same time in an article. No need to be too serious on this. Language is changing, at a slow pace. — Preceding unsigned comment added by Sdxu (talk • contribs) 06:36, 15 January 2015 (UTC)

On a glance, there is no mention of how SD pronounced in article, or there is really an official pronunciation? How about the a or an SDIO? SDHC, SDXC? Just make it consistent and it'll be ok. Sdxu (talk) 06:43, 15 January 2015 (UTC)

While going to excuse, I think about this story and got the answer why I read the long form: I have been reading computer or Microsoft material in these 18 years, about 10,000 pages. And there is lots of acronyms, maybe 100, even in 1 single 1000-page book. Some only mentioned once, twice, or times I can count. And they are similar and sometimes short, 2 letters, 3 letters, or even the SAME. There is no use to talk in acronyms, even to another who is familiar with Microsoft's: we can't catch the acronyms in talking (at first). So I changed to read the long form for ALL acronyms not instantaneously recognized. That's why I read the long form in SD. Hope it adds info to your journey in a and an. Sdxu (talk) 07:45, 15 January 2015 (UTC)

Since they lack vowels immediately after the "S", saying one letter at a time is typical, like "S" - "D", or "S" - "D" - "H" - "C". • Sbmeirow • Talk • 08:16, 15 January 2015 (UTC)

Good Article Nomination?

Came across this article in my regular course of reading and think it deserves to be nominated for a Good Article. Thoughts regular editors? Sam.hill7 (talk) 19:26, 11 March 2015 (UTC) comment added by Sam.hill7 (talk • contribs) 03:45, 16 January 2015 (UTC)

SDIO, SDHC and SDXC

I just made a modest merger of three short paragraphs on SanDisk announcements of successively higher-capacity devices, but it strikes me that the section has become a long catalog of company product announcements with declining relevance to the reader. In fact, some of the earlier announcements will lead no one to read the citation in the footnote because some of these products must have been retired by now. Someone with better understanding of the technology's real milestones (and dead ends) should pare this down. Spike-from-NH (talk) 12:34, 9 March 2015 (UTC)

FAT32X

I am in a revert tussle with Be..anyone. I presume (though do not know for sure) that the two successive list items seek to distinguish between an SD using FAT32 and an SD using FAT32X. I post-edited him with a piped redirect, to make the link he edited continue to appear as "FAT32X" but he said this was a BAD bypass redirect. FAT32X redirects to FAT32, but is nevertheless what this article should have in this position, which doesn't depend on whether a unique page exists. More knowledgeable editors need to give opinions at this point. Spike-from-NH (talk) 01:15, 23 April 2015 (UTC)

I bypassed the redirect, and so it was my bypass that would be bad if FAT32X could be something different from FAT32 now ending up at exactly the same section. The difference is only the partition type for LBA already covered here and again at the redirect target. It's exactly the same file system, and on GPT disks (no MBR/EBR) or superfloppies (no partitions) the different MBR/EBR partition types don't exist. –Be..anyone (talk) 07:18, 23 April 2015 (UTC)

Yes, they appear to be "exactly the same file system," but the article on FAT32 says that "FAT32X...indicate[s] usage of LBA disk access instead of CHS." I assume the previous editor meant something by writing [[FAT32X]] in this one case, and that is why I corrected your correction to say [[FAT32|FAT32X]]. Spike-from-NH (talk) 10:53, 23 April 2015 (UTC)

x86 systems not supporting LBA and limited to CHS are twenty years old and long dead. The devices supporting Secure Digital memory cards are not affected by old x86 history and 16-bit arithmetic. There is only one semi-official FAT32 specification, published by Microsoft for the purposes of UEFI. The FAT32X term is a marketing term used by two vendors of partition software, nobody else needs this WP:NEO for any practical purpose. –Be..anyone (talk) 07:26, 24 April 2015 (UTC)

Free formatters

80.1.145.168 reports/asks in the text of the article:

There are several free PC applications available online for formatting USB drives such as HP USB Disk Format Tool , 2Tware Fat32Format , and miniAide Fat32 Formatter. Does this imply that exFAT is NOT so mandatory as stated here. Is the said mandatory FS a commercial 'deal'?

I am not sure a list of software tools should be in the text of the article, but am sure a broadcast to other editors should not be. On the query itself: In general, the existence of pirate software does not imply that piracy is now acceptable. Two of the tools refer in their names to FAT32, which makes no assertion about exFAT. If these tools are mentioned on a sandisk.com page and if they support exFAT, it may mean that the conditions for use of exFAT have changed, but I don't know that. Spike-from-NH (talk) 16:17, 28 June 2015 (UTC)

Copy protection

I don't understand how the copy protection can work. When the card sends out the data, it can neither tell nor control if the data is just displayed / played or copied to another card or drive. — Preceding unsigned comment added by 82.139.82.82 (talk) 03:21, 8 July 2015 (UTC)

As I understand it, the card refuses to "send out the data" under protection until the requesting software identifies itself with reference to information in the reserved area of the card, using an op-code that is not in the public specification. The size of the reserved area gives the card the ability to require a different authorization for each transaction and makes it harder for unauthorized software to pose as the correct software. Spike-from-NH (talk) 14:32, 9 July 2015 (UTC)

Confusing sentence about guarantees of limits

It is said in this article:

> Compliance with a higher speed rating is a guarantee that the card limits its use of the "busy" indication.

That doesn't seem to make any sense. Limits its use of the busy indication to what? 91.2.78.8 (talk) 19:22, 14 January 2016 (UTC)