Customer Review

Reviewed in the United States on February 19, 2019
I got this card for my galaxy S9. It had a very good chip installed in it before (Samsung 256G Evo Select) which I liked. But I wanted to max out my S9 both in its 400G max capacity and in the speed to record. This chip/card does record 1080p 60fps with no problems at all. It also does 4k video well. (I tested it in one of my cameras.)

The only place it fails is when I'm doing rapid burst pictures in my phone. The camera says it can't do rapid burst when using an external card and switches burst control over to internal memory automatically. But to be fair the Samsung chip I had did that too. So apparently it's something built into the camera app or S9 hardware path that just assumes no external chip can do it, even though both the original Samsung 256G and this even higher spec Sandisk 400G are top of the line spec wise. Not really a problem for me as I don't generally take bursts of photos but mentioned it here in case you do. Frankly, if I needed that, I would get an SLR camera instead of using my phone.

When I tried this memory in my Sony video camera, (which is only supposed to support 256G), it saw all 400G and it worked flawlessly and I filled it with combinations of pictures and videos.

I also tested this card as an external chip in a USB 3.1 adapter with my computer. It showed 155MB/s read and 88MB/s write at 64k transfer sizes for a duration of its entire 400G. That's close enough to its listed max speed and I'm happy with that. Now you need to understand, that's testing with all conditions being nearly perfect for this chip. It's highly unlikely to perform that good in the real world moving your data around. I noticed that if you go below 64k file transfer sizes or don't use high speed ports like USB 3, you see much less speed. Most newer cameras and phones will best utilize the higher speeds. But if you use this card with older SD adapters or USB 2.x or computer SD card readers you'll be disappointed with any fast SD memory card. ALL the pathways through adapters and ports and cables and hardware have to support the higher speeds or testing will just show you the top speed of the weakest link in your data pathway.

But let me tell you this card is amazingly fast to copy files to or from if you have the proper equipment to support it!

When I got this chip, I first removed my Samsung 256G and installed this card instead (blank). Although it showed up right away as 400G in the S9 phone, I had the phone reformat it anyway as I just like to be sure its setup by the particular device before testing.

I then used a USB3.1 adapter to plug the phone into a USB3.1 port on my computer. I already had done driver setups for this phone before.

I decided to fill the 400G card with music videos and some personal videos and my docs and my sound files and music. I setup a single copy from the PC to phone external memory of about 340G. (The card actually formats to 367 computer G even though that's 400G of real memory.) Last time I did 256G like this, it took me few hours to complete. So I started the copy to the phone and walked away thinking I'd come back in several hours or if I heard an error beep. I did notice it was copying files fast.

After about an hour and 15 minutes, I heard a bleep from the computer saying it was done. I was a bit frustrated because I thought I was hearing an error beep. So I began to check where in the copy had died. What I discovered was, it really had copied all 340G in 1.25 hours! I couldn't believe it and rechecked to see all the files were indeed there! That's including almost 200,000 photo files that usually slow down backups or restorals to a crawl. Never had a write of major data speeds be so fast!

So in case you can't tell by now, I love this card in my Galaxy S9 phone. I was happy with the Samsung 256G memory card but thrilled even more by this Sandisk 400G upgrade in speed and storage size. Granted, I have 6TB of media storage alone on my PC that I'll never get all of on a phone. But now, thanks to this card, I've got all my docs, sound files, music videos, and unwatched videos ready to watch on the phone. Couldn't be much happier with this Sandisk 400G Extreme microSD card.

One thing you should be aware of though is you will definitely use your device battery up quicker with this card installed. It sucks my Samsung Galaxy S9+ battery down about 40% faster the the 64G internal memory by itself. But even then, it still stays up most of the day and night before charging. Of course if you do a lot of copying or moving files, it's likely to last slightly less without recharging.

Update December 2020:
This card is still working great for me and it was transfered to my new LG Wing phone. This card is used heavily and still going almost 2 years later. Was a very good buy!
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