I have a new Nokia N810 Internet Tablet, into which I'd like to slot an appropriate memory card, and an N95 Phone with a 4 GB microSDHC card already slotted in. As Oscar Wilde had it, "The pure and simple truth is rarely pure and never simple." So in the interests of establishing some truths about the available options, I'd like to ask for some help in answering the six questions below. And I hope this thread (or what it becomes) may be useful to others pondering the same memory card pre-purchase dilemmas.


A. Form Factor
As I understand it, the N810's card slot is miniSD in size and shape, and SDHC-compliant – which means it takes SDHC cards (Secure Digital High Capacity, SD 2.0). So it can take either a miniSDHC card, or a microSDHC card in a miniSD-sized adapter. Market research (up to 12 Feb 08) seems to indicate:
(a) miniSDHC card capacities only goes up to 4 GB (BTW, anybody know why?); and
(b) microSDHC card capacities are on the up and up: 8 GB cards available now, SanDisk's 12 GB card available from mid-Mar 08, and a 16 GB SanDisk card slated for Mar/Apr 08.
So I'd like to choose the 'microSDHC card in a miniSD-sized adapter' option, and that begs a question regarding those adapters.

• Q1. Since there are miniSD and miniSDHC cards, are there also miniSD and miniSDHC adapters? Or are all miniSD-sized adapters generic, ie: serving up the full memory capacity of the microSD/microSDHC inserted into them to the SDHC-compliant N810 into which they are slotted?

• A1. All miniSD-sized adapters are generic pin-converters, mapping from small to large, ie: they all serve up the full memory capacity of the microSD/microSDHC card inserted into them to the SDHC-compliant N810 into which they are slotted. [5] Most microSD cards now ship with micro-to-mini and micro-to-full SD adapters, allowing you to use the microSD card in ANY size SD card slot. [7]

B. Capacity
It seems from the above like a microSDHC card in a miniSD-sized adapter would be the route to take to get the highest memory capacity. BTW & FYI, any microSD card with a capacity of more than either 2 GB is a microSDHC card (or perhaps it's more than 4 GB – even the SD Card Association's own website is inconsistent [1] in this point). The trouble is, sometimes there's no mention of which type a particular card is on a retailer's product page, or the logo on a HC card itself [2] only says microSD (misleading, and only half true) rather than microSDHC (correct).

So, erm... if a 3 GB card existed, would it exist in a quantum superposition of being *BOTH* an SD card *AND* an SDHC card, until you actually tried to use it, thereby collapsing its waveform into the wrong type of card for your slot? (a little joke diversion for the physics geeks there, sorry).

Since "data expands to fill the available memory" (Parkinson's Law of Data) – or "the quantity of spare memory available is inversely proportional to time" (dalinian's corollary) – then there's no such thing as 'too much memory' in my book (or tablet). So I'd like to get the highest capacity card available.

• Q2. Is there a practical upper ceiling or theoretical limit to the data capacity of microSDHC cards that the N810 will accept?

• A2. There is no difference, to a device, in a 6GB microSDHC and the upcoming 16GB microSDHC cards. There is only a difference in microSD and microSDHC, if that makes sense. There is no physical difference, only software compatiblities. [7] See also A4 below.

C. Interoperability – N810 / N95 / Computer+microSDHC-card-reader
The N95 tech spec says, "Memory card slot supporting up to 4 GB microSD memory cards". And yet posters at discussions.nokia.co.uk say, "I have a 6Gb SDHC from Sandisk. Works fine," and "Just bought 8GB sandisk SDHC and it works fine." And an N95 FAQ [3] answers, "Does the N95 support 8 gig microSD cards?" with, "Yes and it has been said that it should support up to 32 gigs."

• Q3. Are Nokia being "economical with the truth" in claiming the N95 only supports microSD card capacities up to 4 GB? And if so, why? Is it in fact SDHC-compliant, like the N810?

• A3. The N95 is advertised to only support 4GB because when the original N95 was released, it was not capable of using the HC cards. It was through a subsequent firmware update that SDHC cards were supported, and Nokia has chosen not to update the plethora of places in which this is written/recorded, and so leave it up to users to discover. The N95 is currently capable of using MicroSDHC cards up to 8GB. [7] SanDisk currently recommends their 8 GB microSDHC card for N95 users. [9]

• Q4. Is there ANY practical upper ceiling or theoretical limit to the data capacity of microSDHC cards that the N95 will accept?

• A4. Theoretical limit: the microSDHC card is based on the SDA 2.00 specification, introduced by the SD Card Association, which enables SD cards to reach higher capacities: 4GB - 32GB. [8] Practical limit: 8 GB cards available now, SanDisk's 12 GB card available from mid-Mar 08, and a 16 GB SanDisk card slated for Mar/Apr 08. [10] 32 GB microSDHC cards will no doubt follow, all in good time.
  

D. Speed
This subject is very well addressed on the wiki page 'Memory Cards: Is Speed Important?' on 'internet tablet talk' [3]. SDHC cards have SD Speed Class Ratings which specify the following minimum sustained write speed on to empty SDHC cards:
– Class 2: 2 MB/s
– Class 4: 4 MB/s
– Class 6: 6 MB/s
Note that these ratings say nothing about how fast you can read from a card, but it is safe to expect to be able to read faster (maybe much faster) than you can write to an SDHC card.

BUT... most retailers don't mention Speed Class Ratings in describing the cards they sell, and only some cards include a Speed Class Rating logo on the card itself: the number 2 or 4 or 6 enclosed in a capital 'C' character [4], with an optional 'CLASS' prefix.

• Q5. If a Speed Class Rating is (a) missing in a retailer's card description; and (b) not shown by a speed logo on the card itself; then (c) is there any easy way of finding out what IS the Speed Class Rating of a particular card?

• A5. No there isn't. [6]

E. Logo Inconsistencies
The SD Card Association develops and publishes technical standards for SD Card technology, and 'promotes' the use of the technology. But given the inconsistencies on the SD Card Association's own website [1], it's not too surprising that manufacturers are inconsistent in their use of type logos [2] and speed logos [4] on the cards they produce – both of which contribute significantly to the pre-purchasing confusion of consumers.

• Q6. Is only buying SD cards that best meet the SD Card Association's logo regulations the best way for regular consumers to encourage the proper use of type and speed logos in the cards themselves? Or is a consumer-led, mass emailing campaign targeting logo-infringing manufacturers a better idea? (BTW & FYI – I'm NOT volunteering to spearhead such a campaign! Life's too short, I'm pedantry deficient, ... things of that nature, generally.)

• A6. Yes, do buy SD cards that best meet the SD Card Association's logo regulations, but forget about a campaign. [6]

Thanks in advance for your attention, time and attentiveness to detail in clarifying these issues for this bemused consumer. Maybe a sticky post, a wiki page or some FAQ entries may come out of all this? If I don't lose the will to live first ;-)


References

To Questions
[1] Any microSD card with a capacity of more than either 2 GB or perhaps 4 GB is a microSDHC – even the SD Card Association's own website is inconsistent; eg:
(a) "SDHC (above 2GB) must have both the SDHC and the Speed Class logo" at http://www.sdcard.org/about/sdhc#1
(b) "The SDHC Logo is used for cards 4GB or higher in http://www.sdcard.org/home/img001.gif

[2] SD or SDHC logo on the card itself – see 'About SDHC Memory Card' at http://www.sdcard.org/about/sdhc#1

[3] The 'internet tablet talk' wiki page 'Memory Cards: Is Speed Important?' – http://www.internettablettalk.com/wi...d_Important%3F

[4] SD Speed Class Rating logos – here's what they should look like, according to the SD Card Association: http://www.sdcard.org/about/sdhc/sd_Comp_01.jpg


To Answers
[5] pixelseventy2 http://www.internettablettalk.com/fo...61&postcount=3

[6] linux_author http://www.internettablettalk.com/fo...52&postcount=2

[7] rcadden http://www.internettablettalk.com/fo...16&postcount=5

[8] Sandisk, High Capacity for SD Family, SDHC1.pdf http://www.sandisk.com/Assets/File/pdf/retail/SDHC1.pdf

[9] Sandisk, Product Compatibility, Nokia N95 http://www.sandisk.com/Compatibility...Nokia-N95.aspx

[10] 'Sandisk 12 GB microSDHC card (pre-order') http://www.uk-mobilestore.co.uk/prod...roducts_id=927 and 'Technology: 16 GB MicroSDHC cards are on the way!' http://www.symbian-freak.com/news/00...on_the_way.htm