[Defy Q&A, Help & Troubleshooting] DefiAnt2:
Hello All,

I know there are lots of threads here about which SD cards work with the Defy, and which don't... E.g.:

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However, as an experienced computer hardware tech, it all seems very back-to-front to me. When you buy a new PC motherboard, the manual invariably tells you what memory type it requires, what speeds it can handle, and what its maximum memory data transfer rate is. Then, you can simply go out and buy the fastest memory the motherboard supports, and be fairly sure of two things: 1: it's going to work, and 2: you'll have the fastest memory speed you can get out of the motherboard, without wasting money buying faster memory than it can utilise.

For those who don't really understand these things, every motherboard, every CPU, every memory controller and every memory module has a maximum rated speed [over-clocking not included!] at which it is 'guaranteed' to work and be reliable. If your motherboard/CPU/memory controller has a maximum rated 800MHz memory transfer rate, there is no point installing 1333Mhz memory in that motherboard, because the motherboard will only run it at 800MHz. You'll pay more, for no speed or reliability advantage. In fact, as this forum shows, there is a VERY GOOD chance that you'll end up with something that is less reliable. This is because, as chip speeds increase, of necessity, certain timings and timing relationships change. For example, "Data Hold" times may [probably will] decrease, meaning that when reading data back from a faster memory chip, the data is starting to "disappear" from the output pin, before the CPU has had time to properly read it. The data transfer becomes "marginal", meaning it only just works, or doesn't quite. This will result in memory read errors (which will look like data corruption, even though the data inside the chip is perfectly correct), and will result in many of the problems described in these various threads. It will probably vary, depending on temperature, supply voltage, and type of data transfer (e.g. Photo/Video/USB, etc) and even phone - I.e. One Defy might work, the next might not - or your system (PC, phone, etc) may work for some things but not others, or work when it's cool, but bomb out as it gets hot, or vice versa. Instability and Unreliability are the keywords!

This, I submit, is why many people with Class 10 SD cards report problems. They would, I believe, be far better to buy Class 6, and are probably living under the illusion that a Class 10 card will work faster. I would say, it almost certainly won't...

Anyway, my point is, why do phone makers (or Motorola at least as I haven't really looked at other manufacturers) not publish their phone SD Card slot specifications? I just don't understand why not. It seems so fundamental to me.

If they did, you (everyone) would know what card Class to get, and be confident that it should work, and that if it doesn't, you've got a dodgy card. We wouldn't need long threads on XDA Developers discussing which cards work, and which don't.

So, my Defy came (OEM) with an unbranded 2GB micro SDHC card, with no visible Class mark. I wanted to upgrade, so I searched the Motorola Manuals for the SD Card slot spec, to find out what Class I needed. AMAZING, but No Luck! I couldn't find it anywhere.

So I looked at a cellphone accessory suppliers website, to see what they offered.

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Nearly all cards listed for the Defy are Class 4, so I figured the Defy must have a Class 4 slot.

I bought a 32GB Class 4 ADATA micro SDHC card, locally. It worked, no problems. I have tested it fairly thoroughly, copied a couple of GB of data to it (over USB) and done a bitwise comparison of the data. No problems. I have taken and viewed photos and movies, and seen no problems. I also tested the memory speed (using SD Tools from Google Play). It gives Write speeds of around 6MB/s and Read around 15MB/s.

However, while I was there, I spied a clearance priced 4GB Class 6 card, so bought that too. (Also ADATA.) Haven't tested that so much, but did run the same speed test in the same Defy phone. Was disappointed to find that the Write Speed is over 9MB/s (though Read is still around 14-15MB/s.)

From this, I conclude that the correct speed Class for the Motorola Defy SD card slot is actually Class 6 (and that I should have bought a Class 6 card... :( )

Can anyone tell me whether this is correct, and where, if anywhere, the actual manufacturer's SD card slot spec's are published?

BTW, the original 2GB card looks, from SD Tools, to be a Class 4 card, though oddly, the speed seems to vary a lot with that card. It sometimes, at the start of the test, goes as high as 10MB/s, but usually stabilises and ends at about 5.6MB/s (Write speed).

Also, can anyone with a Class 10 card (that works) in their (Original model) Motorola Defy please report here what data Write and Read speeds SD Tools reports? I think everyone with a Defy who wants to upgrade their memory would be very interested to know!

I think it would be great to finally nail this issue down.

Regards,

D2