Digital cameras and camcorders employ memory cards (flash-based removable media) for storage of captured content. There are different varieties of memory cards catering to various performance levels. CompactFlash (CF) became popular in the late 90s, but, has now been overtaken by Secure Digital (SD) cards. Many computing systems (PCs as well as smartphones) also support SD cards for augmenting local storage capabilities. High-end recording systems with fast storage requirements use CFast and/or XQD cards. We recently started in-depth evaluation of the performance of various memory cards. SanDisk sent us a SDXC, two microSDXC, a CFast 2.0, and a CompactFlash card from their portfolio for review.


SanDisk / Western Digital is one of the very few flash product vendors who manufacture their own flash memory. They have a comprehensive flash product portfolio targeting the content creators market. Their portable external SSDs and high-performance thumb drives take care of the post-ingestion portable storage requirements, while their range of memory cards service the actual in-camera storage market. Lexar (which used to be a division of Micron) has memory cards for all formats currently in use - SD, microSD, CompactFlash (CF), CFast, and XQD. SanDisk targets all formats other than XQD.

SanDisk sent 5 different cards for our evaluation:

  • SanDisk Extreme microSDXC UHS-I 128GB
  • SanDisk Extreme PRO microSDXC UHS-II 128GB
  • SanDisk Extreme PRO SDXC UHS-II 128GB
  • SanDisk Extreme PRO CompactFlash 128GB
  • SanDisk Extreme PRO CFast 2.0 64GB

Each of these five cards were subject to our comprehensive memory card evaluation routine. Readers will get an idea of the out-of-box performance as well as how the performance degrades after extensive usage.

The next four sections will detail the obtained performance numbers. Prior to that, we take a look at the testbed setup and evaluation methodology.

Testbed Setup and Testing Methodology

Evaluation of memory cards is done on Windows with the testbed outlined in the table below. The USB 3.1 Type-C port enabled by the Intel Alpine Ridge controller (It connects to the Z170 PCH via a PCIe 3.0 x4 link) is used for benchmarking purposes on the testbed side. SD and microSD cards utilize the Lexar Professional Workflow SR2 SDHC / SDXC UHS-II USB 3.0 Reader. A microSD to SDXC UHS-II adapter is used for the latter. CF cards utilize the Lexar Professional Workflow CFR1 CompactFlash UDMA 7 USB 3.0 Reader. The readers were placed in the Lexar Professional Workflow HR2 hub and uplinked through its USB 3.0 port with the help of a USB 3.0 Type-A female to Type-C male cable. CFast cards utilize the Lexar Professional Workflow CR2 CFast 2.0 Thunderbolt/USB 3.0 Reader via its Thunderbolt 2 port. The testbed connection was made through the Thunderbolt 3 to Thunderbolt adapter.

AnandTech DAS Testbed Configuration
Motherboard GIGABYTE Z170X-UD5 TH ATX
CPU Intel Core i5-6600K
Memory G.Skill Ripjaws 4 F4-2133C15-8GRR
32 GB ( 4x 8GB)
DDR4-2133 @ 15-15-15-35
OS Drive Samsung SM951 MZVPV256 NVMe 256 GB
SATA Devices Corsair Neutron XT SSD 480 GB
Intel SSD 730 Series 480 GB
Add-on Card None
Chassis Cooler Master HAF XB EVO
PSU Cooler Master V750 750 W
OS Windows 10 Pro x64
Thanks to Cooler Master, GIGABYTE, G.Skill and Intel for the build components

The full details of the reasoning behind choosing the above build components can be found here.

SanDisk Extreme PRO SDXC Performance
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  • peevee - Wednesday, November 8, 2017 - link

    Very useful, thanks!
  • ET - Wednesday, November 8, 2017 - link

    How do you explain the Extreme MicroSD's write performance in apps? Caching? It's way ahead of the pack for application use and costs a fraction of the Pro's price.
  • ganeshts - Wednesday, November 8, 2017 - link

    Yes, it was anomalous, and I have to say caching was responsible. I repeated the test sequence thrice with testbed resets inbetween, but the numbers were always similar. Unfortunately, without any way to confirm caching as the issue, I couldn't mention that in the review text.

    Also, note that the Extreme microSD is A1-class, and other microSD cards weren't optimized for the new performance class. So, the controller firmware could be responsible too.
  • imaheadcase - Wednesday, November 8, 2017 - link

    I had to get one of these Extreme Pro versions for my 1080p 60fps camera. Even with it i get the dreaded "writing data to disk please wait" shown on camera when using it.

    I suspect SD cards for video are going to be replaced by something else like a pure micro SSD.
  • imaheadcase - Wednesday, November 8, 2017 - link

    Speaking of memory cards, do you know why you can't read multiple ones at a time in win 10? Also how come you can't by a reader for multiple ones at a time? You can by hundreds of those "all-in-one" doggles but can only read one at a time in windows 10 for some reason..
  • DanNeely - Wednesday, November 8, 2017 - link

    Is it just a W10 issue, or are you limited the same way in other OSes?
  • imaheadcase - Thursday, November 9, 2017 - link

    No other OS to try on. But I'm not sure when Win10 would even do this. Unless for some reason its not allowed simply because of saturated bandwidth if more than one.
  • ddrіver - Sunday, November 12, 2017 - link

    For me it works fine. My preactivated ISO has some extra mods and stuff integrated so maybe that fixes it...
  • "Bullwinkle J Moose" - Wednesday, November 8, 2017 - link

    With the lack of information you provided, we could only guess

    Are you trying to read 2 cards from a single USB port or hub?
    That would be a problem

    Have you tried 2 separate card readers on two independent USB ports?
  • "Bullwinkle J Moose" - Wednesday, November 8, 2017 - link

    Yes, you CAN buy hundreds of all-in-one dongles but you can only read one card at a time on a single port!

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