Click here to go to our new forums at http://tw.forumosa.com
If you are a Forumosan Regular, when you log in for the FIRST TIME, you must RESET your password by using the Password Recovery system.

Usernames on the new forums must not contain any SPACES and must end with LETTER or a NUMBER; if yours does, you will be prompted to change your Username
Contact us at admin(at)forumosa(dot)com or @forumosa on Twitter or on our Facebook Page if you have any questions or problems logging back in

Be careful with SD cards bought here

Moderator: Mick

Be careful with SD cards bought here

Postby dylanh724 » 09 May 2016, 18:35

At that IT "yellow store" you always see throughout Taipei that sells electronics and gadgets --

I bought 2 SD cards from there before and both were not what they actually said they were.

The 1st one ended up being some company I never heard of, but was mfg'd in Taiwan, when it was suposed to be Verbatim, according to a few apps that test for genuine sd cards. This was maybe 6 months ago.

The 2nd one I bought, about 5 minutes ago, was an adata 64gb uhs class 10 card - but it's actually a sandisk that runs at 1/3 the advertised speed
Founder of Imperium42 Game Studio
Developer of flagship title, "Throne of Lies: The Online Game of Lies and Deceit" @ https://www.ThroneOfLies.com
>> Give us a +1 @ http://greenlight.ThroneOfLies.com :)
User avatar
dylanh724
Memorized My Password (gāng jìhǎo zìjǐ de mìmǎ)
 
Posts: 46
{ AUTHOR_TOPIC }
Joined: 29 Dec 2013, 23:05
In Taiwan since: 20 Aug 2013



Re: Be careful with SD cards bought here

Postby milkalex » 09 May 2016, 20:02

bring it back then!
milkalex
Chinese Class Dropout (Zhōngwén kè zhōngchuòshēng)
Chinese Class Dropout (Zhōngwén kè zhōngchuòshēng)
 
Posts: 754
Joined: 01 Aug 2008, 20:15



Re: Be careful with SD cards bought here

Postby MPenguin » 03 Jun 2016, 09:47

Stick with Sandisk.
MPenguin
Chair-throwing Legislator (rēng yǐzi de lìfǎ wěiyuán)
Chair-throwing Legislator (rēng yǐzi de lìfǎ wěiyuán)
 
Posts: 316
Joined: 21 Jul 2008, 11:01



Re: Be careful with SD cards bought here

Postby hansioux » 03 Jun 2016, 10:21

SD card's speed isn't constant. It depends on the workload and the condition of the NAND flash memories inside the card. Manufacturer would only put sequential read/write speeds, usually on bare-metal testing platforms, on the package. As there's less free space on the card, and as the card begins to wear out, the speed would decline, sometime rapidly, especially when the card needs to perform background GC or wear-leveling for its SD cards. Testing it with a full OS system would also decrease it's throughput.

By the way, bigger size usually means the NAND chips were made by a more advanced fabrication technology node. While "advanced fabrication" may sound good, it what it really means is that each memory cell is made smaller, with less capacity to store electrons, making it harder to write and more prone to data loss. "Larger capacity" usually means instead of storing one bit of data on one memory cell, now they are storing 2 bit of data, with a technology called MLC. MLC also makes it harder to write and more pron to data loss. So to make sure users don't notice all that data corruption, they added ECC, to repair all the corrupted data so you wouldn't notice the "advance" of technology.
Don't confuse me with your reasonableness.
User avatar
hansioux
Thinking of Staging a Coup (xiǎng yào gǎo zhèng biàn)
Thinking of Staging a Coup (xiǎng yào gǎo zhèng biàn)
 
Posts: 6457
Joined: 28 Jul 2012, 14:41
In Taiwan since: 30 Jun 2006



Re: Be careful with SD cards bought here

Postby finley » 03 Jun 2016, 10:56

I think they're up to 4 bits per cell now.

Also worth mentioning that all the chips inside come from a very small number of manufacturers. NAND Flash ICs have a very low profit margin and demand cutting-edge equipment to keep up with Moore's Law expectations. Only the big boys can afford to make them. So if it says 'Sandisk' or 'Adata' on the outside, that tells you little or nothing about the IC inside. I think Sandisk develop their own ICs in co-operation with Toshiba, but lesser-known brands will use whatever they can get for the lowest price.

A few years ago there were 'fake' NAND Flash ICs floating around - salvaged production rejects and suchlike - although I think this is virtually unheard-of now.
"Global warming is happening and we KNOW that man is 100 percent responsible!!!"
- Fred Smith
User avatar
finley
Entering Second Childhood (èrdù tóngnián qī)
Entering Second Childhood (èrdù tóngnián qī)
 
Posts: 7145
Joined: 20 Jan 2011, 23:34



Re: Be careful with SD cards bought here

Postby hansioux » 03 Jun 2016, 11:22

finley wrote:I think they're up to 4 bits per cell now.


Right now TLC (tri-level cells) is the most common after MLC. MLC can be misconstrued to be 4 bits per cell, because it essentially divides a cell's threshold voltage window into 4 levels, for 00, 01, 10 and 11. Traditionally, SLC cells just need two states, 0 and 1. TLC needs 8 states. It's common on large capacity SSDs, and as you can imagine, data isn't going to be safe on large capacity SSDs for too long.

In the old SLC days, the commercial claim is that data is going to be safe for 10 years. Manufacturers have since stopped making that claim for MLC and TLC devices.
Don't confuse me with your reasonableness.
User avatar
hansioux
Thinking of Staging a Coup (xiǎng yào gǎo zhèng biàn)
Thinking of Staging a Coup (xiǎng yào gǎo zhèng biàn)
 
Posts: 6457
Joined: 28 Jul 2012, 14:41
In Taiwan since: 30 Jun 2006



Re: Be careful with SD cards bought here

Postby finley » 03 Jun 2016, 22:12

nope, it really is 4 bits per cell:

http://www.spansion.com/Products/Docume ... epaper.pdf

Although it's arguable if the storage cell is really a single cell in this architecture.

mad, innit? I remember when a 32kB EPROM cost as much as a modern 32GB NAND IC, with about the same die area.
"Global warming is happening and we KNOW that man is 100 percent responsible!!!"
- Fred Smith
User avatar
finley
Entering Second Childhood (èrdù tóngnián qī)
Entering Second Childhood (èrdù tóngnián qī)
 
Posts: 7145
Joined: 20 Jan 2011, 23:34



FRIENDLY REMINDER
   Please remember that Forumosa is not responsible for the content that appears on the other side of links that Forumosans post on our forums. As a discussion website, we encourage open and frank debate. We have learned that the most effective way to address questionable claims or accusations on Forumosa is by engaging in a sincere and constructive conversation. To make this website work, we must all feel safe in expressing our opinions, this also means backing up any claims with hard facts, including links to other websites.
   Please also remember that one should not believe everything one reads on the Internet, particularly from websites whose content cannot be easily verified or substantiated. Use your common sense and do not hesitate to ask for proof.




Return to Technology



Who is online

Forumosans browsing this forum: No Forumosans and 0 guests