Why your laptop’s SD card reader might be terrible

8 min read

[responsivevoice_button rate=”1″ pitch=”1.2″ volume=”0.8″ voice=”US English Female” buttontext=”Story in Audio”]

Why your laptop’s SD card reader might be terrible

For content creators, a laptop with a built-in SD card reader is a preferred feature. Some users go so far as to consider laptops only if they have a reader.

One mistake with that choice is it assumes all SD card slots are created equal. Our tests clearly show they’re not. It’s also difficult to know how fast the SD card reader in your laptop is. If SD card speed really matters to you, the best way to get what you want is to buy an external reader whose specs are clearly designated. 

PCWorld put four newly manufactured laptops’ SD cards through their paces. For this challenge we looked at:

To give us a control point, we also recorded the performance of a SanDisk Extreme Pro UHS-II USB 3.0 card reader inserted into one of the Dell G5 15 SE’s USB 3.0 slots.

Because this test would be pointless without a fast SD card, we used a 128GB SanDisk Extreme Pro SD card. The card is a UHS-II card, meaning it rides on the Ultra High Speed II bus and features a second row of contact pins on the back to hit the higher performance ratings of the interface. The UHS-II bus can hit 312MBps in full duplex mode and 624MBps in half-duplex mode. We formatted the card in exFAT, which has seemingly become the standard for most large-capacity SD media.

SD Card Reader and UHS-II Card Gordon Mah Ung

We used a 128GB SanDisk Extreme Pro card rated for 300MBps reads and 260MBps writes for our testing.

The SanDisk Extreme Pro SD Card is rated for read speeds right up to the limit of UHS-II at 300MBps with write speeds rated at 260MBps. 

Why not UHS-III?

If you’re wondering why we’re not using an even faster SD card using the newer UHS-III bus, it’s because we couldn’t find a card that even supported the newer interface, which takes speeds to 312MBps in full duplex mode and 624MBps in half duplex mode. Searching Amazon.com just last week, we saw no signs of a UHS-III card for sale.

(And no, don’t confuse UHS-III (the bus) with the U3 symbol. U3 refers to the card’s “UHS Speed Class” mark for video performance of a camera and card. Yes, they seriously have U3 and UHS-III which don’t mean the same thing. U3 has largely been supplanted by the newer and slightly less confusing “V” video speed class mark.)

We contacted SanDisk to ask why it wasn’t offering a newer UHS-III bus card. Company officials said it’s largely concentrating on the even faster SD Express standard, which has a speed limit of 3,940MBps.

Laptop SD Card slot performance

All four laptops feature integrated card readers, but performance varied greatly, as you can see from our first test, Crystal Disk Mark’s default sequential read test. The Dell XPS 15 9500 comes out in front by a fair margin over the XPG Xenia 15 and Dell G5 15 SE, but it’s very close to the Gigabyte Aero 17.

sd slots cdm7 read IDG

Aero 17 and XPS 15 9500 users can be happy they’re getting awesome read performance, but you’re probably wondering just why the Xenia 15 and G5 SE 15 are sucking wind. You’ll see the reason if you look at the labels for the laptops above: It’s largely due to the card reader and the interface they’re connected to. 

For the worst laptop here, the Dell G5 15 SE, it’s likely gated by the USB 2.0 interface it’s hooked up. USB 2.0 has a maximum theoretical speed of 480Mbps or 60MBps. Once you account for overhead it’s generally far lower than 60MBps. 

You May Also Like