For some users, the included 64GB or 128GB of internal storage found in the Microsoft Surface Go may not be enough. Thankfully, unlike Apple and its iPad, Microsoft included the option to expand that storage with a microSD slot.

For the purposes of this story, we focused on 64GB memory cards. So which one should you get? The fastest and most expensive (Delkin, $80) or the best-selling and cheapest (Silicon Power, $15)? And what can you do with that card in Windows 10 and the Surface Go?

Check out this new Surface Go guide to microSD cards for answers.

How to expand Surface Go storage using microSD

Using a microSD card on Surface Go is very simple. You just slide it into the slot under the Surface Go's kickstand.

Windows 10 will recognize the drive, and you can begin using it right away. However, if you want to use it for apps, games, and more you need to tell the OS to do so.

What can you do with expandable storage in Surface Go?

Back in the day, SD memory cards were treated merely as external storage that you could keep photos or media on but not install apps or games, limiting their usefulness. By contrast, Windows 10 lets users mainly do anything they want with an SD or microSD card.

By heading to Settings > Systems > Storage > Change where new content is saved, you can choose to have the following put on a microSD card for the Surface Go:

  • New apps.
  • New documents.
  • New music.
  • New photos.
  • New movies and TV shows.
  • Offline maps.

If you already have apps or games installed to the primary drive on the Surface Go, you can navigate to Settings > Apps > Apps & features and move existing software to the newly-mounted microSD card (see above image).

There are limitations, however. So-called Windows 10 "inbox apps" like Mail, Camera, and Calculator, cannot be moved. Likewise, a developer can flag their app or game as not installable to an SD card due to degradation in performance (the popular YouTube app MyTube! is one example).

If you use the app or game frequently, keep it on the main drive and put rarely used apps or games on the microSD card. Even better, try to keep all apps and games on the main drive with just media (music, movies, photos, and documents) on the microSD card, because the performance hit is inconsequential for those items.

The fastest microSD card isn't always the best

Surface Go owners obviously need to pick which card to purchase. Like all flash media, microSD cards range in speeds, class, size, and more.

For this test, we bought three microSD cards to use on the entry-level 4GB Surface Go:

The Silicon Power and Lexar options are both Class 10 cards, but the Silicon Power is Ultra High-Speed Phase-1 (UHS-1), and the Lexar is UHS-II. UHS refers to the bus interface for the SD card, and UHS-II or even UHS-III is faster than UHS-1.

The Delkin is the most expensive and is a UHS-II Video Speed Class 60 (V60) meant for 4K video, high-speed photography, and more. It has theoretical read and write speeds of 285MB/s and 100 MB/s, respectively, compared to the "professional" Lexar with 150MB/s and 45 MB/s.

Going by the rule of computers faster is always better, right?. But splurging for the $80 Delkin likely isn't the best choice here.

Using CrystalDiskMark we measured all three cards for sequential read and write speeds.

microSD card comparison

Device Price Size Read Write
Silicon Power $15 64GB 79 MB/s 44 MB/s
Lexar Pro $60 64GB 85 MB/s 55 MB/s
Delkin $80 64GB 70 MB/s 54 MB/s

While the $60 Lexar is technically faster than the $15 Silicon Power, the price difference hardly justifies the gains. Meanwhile, the most expensive card – the $80 Delkin – had slower read speeds than the $15 Silicon Power on Surface Go.

In real-world file transfers between the Lexar and Silicon, we saw the following results using the Surface Go 4GB with 64GB of eMMC internal storage.

Transfer from card

  • Silicon Power: 1.80GB (2x files) took 33 seconds to eMMC.
  • Lexar Pro: 1.80GB (2x files) took 29 seconds to eMMC.

Transfer to card

  • Silicon Power: 1.80GB (2x files) took 49 seconds to SD.
  • Lexar Pro: 1.80GB (2x files) took 34 seconds to SD.

The Lexar is faster, but the differences are minor.

Surface Go storage speed comparison

The Delkin is a fast card, but it doesn't matter for the Surface Go.

Another real-world test is playing a 10GB MP4 video file in the Windows default video player. Both cards loaded up the video instantly and scrubbing (using the slider to jump to different parts of the movie) works without buffering or delays. There was no discernable difference.

Device Size Type Read Write
Surface Go 64GB microSD 70 to 85 MB/s 44 to 55 MB/s
Surface Go 64GB eMMC 260 MB/s 145 MB/s
Surface Go 128GB SSD 1,185 MB/s 133 MB/s

The Lexar and Delkin are not bad cards. The issue is the Surface Go does not seem capable of hitting more than 85 MB/s for read speeds (and 55 MB/s for write) on any card. That is likely a hardware issue although software or firmware could play a part too.

For comparison, the Delkin, when used with the Surface Book 2 (using the SD adapter), managed a respectable 224 MB/s for read and 69 MB/s for writes, confirming our suspicion about Surface Go hardware limitations.

That makes any purchase of an SD card for use solely with Surface Go with over 105 MB/s (anything above UHS-1/Class 10) not worth it.

Therefore, our recommendation is to buy the cheapest UHS-1/Class 10 micro SD card you can find with the storage amount you want (up to 512GB) for use exclusively with the Surface Go. Buying something that is faster or more expensive does not yield significantly better performance and is a waste of money.

The Silicon Power 64GB card used here has a 4.6-star rating on Amazon, ships free with Amazon Prime, and performs just as well as a more expensive card for casual use with the Surface Go.

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