SanDisk Extreme 64GB

  • Advertised capacity: 64GB
  • Fake/skimpy flash: Skimpy (0.21% skimp)
  • Protected area: 134,217,728 bytes
  • Speed class markings: U3, V30, A2
  • CID data:
    • Manufacturer ID: 0x03*
    • OEM ID: 0x5344 (ASCII: SD)*
    • Product name: 0x534e363447 (ASCII: SN64G)
Sample #123Average
Obtained fromAmazonAliExpressAliExpressN/A
Price paid$10.43$9.60$9.60$9.88
Logical capacity63,864,569,856 bytes63,887,638,528 bytes63,887,638,528 bytes63,879,948,970 bytes
Physical capacity63,864,569,856 bytes63,887,638,528 bytes63,887,638,528 bytes63,879,948,970 bytes
Fake/skimpy flashSkimpy (0.21% skimp)Skimpy (0.18% skimp)Skimpy (0.18% skimp)Skimpy (0.19% skimp)
Adjusted skimp0.0019%-0.03%-0.03%-0.019%
Product revision0x860x850x85N/A
Manufacture dateSep 2023Sep 2023Sep 2023N/A
Serial number0xd84929ad0xfea61ca20xfea61c88N/A
Sequential read speed (MB/sec)85.94165.70159.05136.90
Sequential write speed (MB/sec)51.6869.0074.2964.99
Random read speed (IOPS/sec)3,334.232,910.072,795.223,013.17
Random write speed (IOPS/sec)293.81640.391,154.36696.19
Read/write cycles to first error1,269Not yet determinedNot yet determined1,269
Read/write cycles to complete failureNot yet determinedNot yet determinedNot yet determinedNot yet determined
Total days to complete failureNot yet determinedNot yet determinedNot yet determinedNot yet determined
Card reader usedSanDisk MobileMateJJS CR-UTC4ACJJS CR-UTC4ACN/A
Package frontN/A
Package backN/A
Card frontN/A
Card backN/A

* This manufacturer ID/OEM ID combination is pretty well known to be associated with SanDisk.

Discussion

Continuing my (hopefully objective) evaluation of SanDisk cards, I purchased both the 32GB and the 64GB versions of this card. As I alluded to earlier, I purchased the 64GB version for a very particular reason.

SanDisk has a “gimmick” with some of their cards: they’re UHS-I cards, but SanDisk advertises speeds that are beyond what should be possible under the UHS-I spec. Under UHS-I, the maximum clock speed for an SD card is 208MHz, and SD cards have four lines for transferring data — which means that the maximum possible speed should be 832Mbit/sec, or 104MB/sec. However, this card advertises that it can get read speeds of up 170MB/sec and write speeds of up to 80MB/sec. I don’t know exactly how they do this, but if you look closely at the package, there’s an asterisk: it requires a “compatible device capable of reaching such speeds”. There’s also a note on the front of the package that says “Compatible with SanDisk Professional PRO-READER SD and microSD to achieve stated read speeds”. I suspect that these card readers have some mechanism to detect whether the card is one that should support these higher speeds; if they do, I suspect that the reader simply overclocks the card to get those speeds.

I don’t have one of the SanDisk Professional PRO-READER SD or microSD readers; however, I do have several SanDisk MobileMate microSD readers — and on the package, it says — quite prominently — “Enables SanDisk enhanced UHS-I microSD card speeds”. This should mean that I should be able to use this reader with this card and get the speeds they advertise (or close to it), right? Well…nope. Actual read/write speeds only got about halfway to the maximum stated on the package.

Compared to the other cards in my collection, sequential read and sequential write speeds were above average, with sequential write speeds being more than one standard deviation above average. Random read speeds were more than one standard deviation above average as well; however, random write speeds were slightly below average. Compared to the other name-brand cards that I tested, sequential read and random write speeds were below average. While this is good enough for the U3 and V30 marks that it carries, the A2 mark requires random read speeds of 4,000 IOPS/sec and random write speeds of 2,000 IOPS/sec — and this card fell well short of that.

Side note: no card I’ve tested so far has met the performance thresholds for the A2 mark. To reach the speeds required for the A2 mark requires some pretty advanced features of the SD spec, which probably requires hardware beyond what I have. However, this card’s random write speeds weren’t even good enough for the A1 mark — and seeing as how I have other cards in my collection that did meet the threshold for the A1 mark, I doubt that it would have performed well enough for the A2 mark even if it had been tested under the right conditions.

Endurance tests for all three cards are still ongoing:

  • Sample #1 suffered several address decoding errors starting in round 1,270. It has survived 4,983 read/write cycles in total. While disappointing that this card couldn’t make it past the 2,000 read/write cycle mark without errors, the number of sectors affected so far has been fairly small (only 114).
  • Sample #2 has survived 4,000 read/write cycles so far and has not yet experienced any issues.
  • Sample #3 has not yet reached the 2,000 read/write cycle mark. It is currently expected to reach this point in July 2024.

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