Speeds of SD Cards - is it reader dependent

[Oldjim]

There are a number of speeds quoted on the Scan listing for Class 10 SDHC cards and my question is whether this speed is reader dependent as I intend to add one to my HP 250 Laptop which only states that it supports SD/SDHC/SDXC Memory Cards and there would be no point in going for a Class 3 if the reader is limited to Class 1

[ik9000]

There are a number of speeds quoted on the Scan listing for Class 10 SDHC cards and my question is whether this speed is reader dependent as I intend to add one to my HP 250 Laptop which only states that it supports SD/SDHC/SDXC Memory Cards and there would be no point in going for a Class 3 if the reader is limited to Class 1

the key thing is to look at the stated Mb/s of the card and the reader. I've seen a mix of "class 10" cards with Mb/s ranging from 35 right up to 95+Mb/s. The SD/HC/XC etc is to do with max GB storage - you tend to hit the buffers there on older machines/readers where the large capacities simply can't be read due to some limitation of addressing the larger volume NAND chips (SFAIK). Provided it can handle the volume a faster card will work in a lower class reader, but its speed may be artifically capped lower than it is capable of. If the machine has a USB2/3 port consider using those with a third party USB reader if the speed/bandwidth would be greater than for the built-in reader.

[Oldjim]

that is the problem as I want to use the internal slot as a permanent storage so that if the laptop or SSD drive fails I can remove it for security but I don't want a USB pen drive attached permanently
there is no information I have found anywhere for the reader so I may have to just get one and see

[ik9000]

that is the problem as I want to use the internal slot as a permanent storage so that if the laptop or SSD drive fails I can remove it for security but I don't want a USB pen drive attached permanently
there is no information I have found anywhere for the reader so I may have to just get one and see

That is probably your best option. Trying to find how many internal lanes are assigned to the reader, what bandwidth they are, and whether they're shared with other ports will be rather difficult for a laptop with a custom motherboard.

[Oldjim]

Update
This link https://kb.sandisk.com/app/answers/d...performance%29

UHS Speed Class was introduced in 2009 by the SD Association and is designed for SDHC and SDXC memory cards. UHS utilizes a new data bus that will not work in non-UHS host devices. If you use a UHS memory card in a non-UHS host, it will default to the standard data bus and use the "Speed Class" rating instead of the "UHS Speed Class" rating. UHS memory cards have a full higher potential of recording real time broadcasts, capturing large-size HD videos and extremely high quality professional HD.

So it would appear that the higher speed card is the way to go as it should use a UHS Host

[BobF64]

So it would appear that the higher speed card is the way to go as it should use a UHS Host

As your Sandisk quote says "UHS cards will operate at UHS speeds ONLY when the card reader is a UHS host".

So for best speeds, you want one that has both UHS and Class 10 (assuming this is still the highest class) and it will perform at the best rate the card reader can do. If HP do not state it is a UHS host conforming card slot, then it probably isnt.

But, it also depends how you use the card.

A high speed, 1 channel card might look good in a single sustained transfer, but not if simultaneous reads/writes are being performed.

[ik9000]

It also depends how much he wants to spend in trying it out to begin with. my old Dell Inspiron (and it is old circa 2006) simply will not read my SDXC cards at all. The user manual suggests the capacity is capped at something like up to 32GB so I'd always put it down to that.

[Oldjim]

Final response - total disaster as the laptop just wouldn't handle it with failure to read quick enough and data corruption among other things so added the 32GB microSD card to a USB Card reader (I already had one) and I now have a relatively cheap USB drive

[peterb]

Just a word of caution, if you are using the SD card as a removable data store (for security) it is still possible for data to be cached on the main drive which could still be readable by someone with the appropriate tools and skill. The risk is slight (unless your drive is specifically rargeteded) but it is something you should be aware of.

[CAT-THE-FIFTH]

Regarding cards most only seem to point out read speeds not write speeds so be weary when purchasing a card.