Computer Hardware Technology


Written by nillo

What Is Memory Card Speed Class Ratings?

If you’ve ever going to buy a memory card you probably saw some sort of speed
marking on it. Whether it says something like “200x” or “UHS 1” or “Class 10” or maybe you’ve heard of these. He didn’t exactly know what they mean. That’s exactly what this post is going to be about. Because a lot of times it’s way more complicated than it needs to be song and explain it in simple terms hopefully.

what is memory card spped class

what is memory card spped class

About Memory Cards Class Ratings And UHS Ratings:

So first let’s get into SD cards. Now SD cards have ratings that describe the minimum read and write speeds of the memory card in terms of megabytes per second. And there are two tiers of speeds. The first one is the regular class, description which is class 2, class 4, class 6 and class 10. And then there’s an upper tier UHS. Which stands for ultra-high speed. And this is going to be either UHS 1 or UHS 3. The regular tier the class number just describes the number of megabytes a second it can reading write minimum. Class 2 is 2MB/s, class 4 is 4MB/s, class 6 is 6MB/s And class 10 is 10MB/s in read and write.

Now there is a distinction for the class 2 foreign 6 those ratings actually describe the minimum stay even if the card is fragmented and all. So even in a worst-case scenario you still get those speeds. But for class 10 that 10MB/s rating is pretty much only if the card is in a non fragmented state. So it’s like a best-case scenario. So in some cases for a class 10 card might get slightly lower than the ten megabytes a second minimum and usually the computer will warn you if the speed is behaving lower than it should be on a class 10 cards. Now let’s move on to the UHS ultra-high speed. These numbers are basically representing multiple of 10 megabytes per second for the minimum read and write speeds. So for example UHS 1 is also a minimum of 10 megabytes a second and UHS 3 is minimum of 30 megabytes per second.


So you’re probably wondering what’s the difference between a class 10 and UHS 1? Well there really isn’t any practically you’re still going to get the minimum of 10 megabytes a second. The only difference is that UHS 1 card use a different Bus interface. That slightly faster and is capable wire transfer speeds. But that won’t affect the performance of the individual card. It shows you basically what the maximum speed any card could go to using that interface. So you can see on this chart there any type of card may use a regular bus interface.

But it’s some of them use high-speed interface. Now don’t get confused with the UHS (1) or UHS (2) interfaces here. The Roman numerals are actually referring to the bus interface not the card speed ratings in this case. So you can see that normal regular speed are capable of 12.5MByte/s and high speed is 25 megabytes a second. However if it’s either of the UHS interfaces, it will be faster than the non UHS interfaces. So the UHS 1 interface is capable of at least 50 megabytes a second and UHS 2 is capable of at least 156Mbyte/s. And again those are just the speed of the interfaces, which describe what cards can take advantage of maximum. But for the actual speeds of the cards you have to look at the speed ratings. So you’re probably thinking this sound like a big mess.

Well let me simplifies. UHS wanting to the Roman numerals described the speed of the interfaces what cards can take advantage of if they’re sufficiently fast. But the UHS rating or the class ratings actually describe the speed of the card it self. So that’s really all you care about. Because that describes how much performance you’re going to get out of the card and you really never have to worry about the speed of the bus interface. The only exception would be if you’re using a very fast SD card like one that’s capable of over 150 megabytes a second then you want to make sure that your card reader has the fastest UHS interface. And that’s really the only time it would apply. But it’s still something to be aware of.

About Memory Cards X Ratings:

Now let’s get to the “X” ratings. you’ve probably seen someone says 500X 1000X but what exactly does that mean? Well this rating in my opinion is the dumbest of them all. Because it’s based on the read and write speeds of compact discs. Yes old CD rom! And in this case the number before the “X” is how many times you multiply 150 Kb bytes per second towards that number to get the final speed of the card. Yes I said KiB. It’s not going to get into the difference between kilobytes but you can kinda think of them as the same thing for this purpose. So basically to get the speed of cardiac new mantra math the multiply 150 times 500 or whatever numbers in front of it. Then convert that to megabytes a second it’s just a pain. And you’ll actually see this system used on CDs printed on CDs will say 48X or 18X that’s what that’s referring to with the same system.
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And I don’t know why they implemented this on sdcard cuz no one seems to know that even means. So, let’s do an example to demonstrate has done this system is if you had a 600X rating card you would multiply that by 150 Kb bytes that give you a certain number of kilobytes what you have to convert megabytes which then gives you about ninety megabytes per second. Which you would have no idea of knowing if you didn’t do the math. And if that didn’t sound dumb enough there’s another reason why this system is extremely annoying. Because that 600X or whatever speed is the maximum. It’s not even guaranteed it’s what it could go up to say yes to consider it probably won’t get up to that speed. And on top of that manufacturers don’t usually specify whether they’re giving a rating in read or write speed. So usually they’ll put read speed because it’s faster. Now fortunately the class ratings which are more simple and guaranteed speeds are the standard for SD card.

I hope I was able to explain it in a way that made sense. So that now going forward you won’t be so annoyed trying to figure out what the ratings means. So if you guys enjoy this article be sure to share this I know you guys enjoyed this article and found it helpful. And if you want to leave a comment for what you guys thought I’m definitely interested that.

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