SanDisk Extreme Pro 512GB CFExpress B Card Review – Understanding Sustained Data Transfer, Temperatures and Thermal Throttling


With today’s new cameras pushing the bar just a bit more, there is a new found need to understand the affect that sustained write speeds have on a cameras ability to record and store digital media..  The Canon R5 is a perfect example because of its ability to film video in 8k and higher 4K resolution.  A card with low sustained write speeds simply will not keep up as that video data is being stored concurrent to filming.  For our testing today it is rather simple, in that, we compiled 45GB in 8K video files and moved them to the disk monitoring the speed..  To confirm this, we also did another transfer from location to location on the SanDisk Extreme Pro CFexpress B Card and confirmed the exact same speeds……just over 751MB/s.

Just as a bit of a comparison, we thought we might test the Lexar Professional once again…


It was at this point that we started to take closer looks at how heat affects performance, and learned that our Lexar result during this test was better than that of our original report because of the fact that our original test was conducted following several other benchmarks.  Both of these results above are tests where the card was at room temperature before the test was conducted.


In testing the SanDisk Extreme Pro CFexpress B Card, we learned how temperature affects the cards performance.  We saw this in our previous ATTO benchmark but wanted to look just a bit more closely so we conducted several tests again watching the temperature with Crystal Disk Info


We learned through this test that the SanDisk Extreme Pro CFexpress B 512GB Card starts to thermal throttle at 65C.  We wanted to see how this affected other benchmarks so threw in a Crystal DiskMark score where the most notable drop was write performance at 485MB/s. We received the same results with respect to sustained write speeds through our AIC card and the card reader, the card reader result shown here.


We decided to follow this with a true data transfer once again and received this:


In testing the Lexar Professional CFexpress, we determined that their thermal throttling doesn’t kick in until just after 80C and only brought write speeds down to about 800MB/s.  We found this interesting, especially with respect to the SanDisk thermal throttling at 459MB/s, as the Canon R5 only requires speeds of 400MB/s for 8K recording.


We have put the SanDisk Extreme Pro beside the Lexar Professional CFexpress B Card for our true to life data testing.  In this test, we simply place 15GB files representing music, video, pictures and operating systems onto the target drive.  We then copy each file from one place on the target disk to another, recording the time taken for the transfer.


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