SanDisk Extreme PRO 64GB

  • Advertised capacity: 64GB
  • Logical capacity: 63,864,569,856 bytes
  • Physical capacity: 63,864,569,856 bytes
  • Fake/skimpy flash: Skimpy (0.21% skimp)
  • Protected area: 134,217,728 bytes
  • Adjusted skimp: 0.0019%
  • Speed class markings: U3, V30, A2
  • CID data:
    • Manufacturer ID: 0x03*
    • OEM ID: 0x5344 (ASCII: SD)*
    • Product name: 0x5352363447 (ASCII: SR64G)
    • Product revision: 0x86

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

Sample #123Average
Obtained fromAmazonAliExpressAliExpressN/A
Price paid$12.99$10.63$10.63$11.42
Manufacture dateSep 2023Oct 2023Oct 2023N/A
Serial number0xa5f89e850xd1e250040xd1024e86N/A
Sequential read speed (MB/sec)86.4387.1984.8686.16
Sequential write speed (MB/sec)60.3452.5662.7158.54
Random read speed (IOPS/sec)2,023.751,755.971,834.401,871.37
Random write speed (IOPS/sec)349.67298.88394.89347.81
Read/write cycles to first error2,034Not yet determinedNot yet determined2,034
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
Package frontN/A
Package backN/A
Card frontN/A
Card backN/A


As with the SanDisk Extreme 64GB, this card makes some pretty extravagant performance claims — which is why I got it. This one’s claims are even more extravagant than the SanDisk Extreme 64GB — it claims you can get read speeds of up to 200MB/sec and write speeds of up to 90MB/sec.

Before I talk about performance, I want to talk a little bit about the card reader I used for this card: the JJS CR-UTC4AC. JJS doesn’t specify which chip they use, but some deduction can tell us which one they probably used. The reader gives its vendor ID as 0x05e3 and its product ID as 0x0764. Vendor ID 0x05e3 belongs to Genesys Logic, Inc. The Linux USB project maintains a list of known vendor ID/product ID combinations; however, this list doesn’t have an entry for product ID 0x0764. We’re not finished yet, however.

If we go to Genesys Logic’s website and look at the list of the card reader controllers that they offer, we see that they offer — as of this writing — 20 different options:

A screenshot from Genesys Logic's website showing a list of card reader controllers they offer.

We can filter out some of these options based on what we know:

  • The last two options — the GL9750 and the GL9755 are PCI Express (not USB), so we can knock them off the list.
  • The three options directly above that — the GL835, GL835T, and GL892S — are only USB 2.0, so we can knock those off the list.
  • The GL3227E and GL3224E are eMMC controllers, so we can knock those off the list.
  • The GL3232, GL3232S, GL3213L, and GL3233T are all single-LUN readers, so we can knock them off the list.
  • UHS-II was added in version 4 of the SD card specification. The GL3230, GL3231, GL3223, GL3224, GL3224L, and GL3235 only support version 3 of the SD card spec, so we can knock those off the list.
  • If we pull up the product page for the GL3239, it only mentions support for version 1.0, 1.1, 2.0, and 3.0 of the SD specification — no mention of version 4.0, which means we can knock this one off the list as well.

This leaves us with only two options: the GL3230S and the GL3231S. The GL3230S is a controller that supports a wide array of memory card types: not just SD/MMC, but also CompactFlash and Memory Stick (and its many derivatives). The GL3231S, on the other hand, only supports SD/MMC (and their derivatives). In addition, the GL3230S is a 4-LUN chip, while the GL3231S is a 2-LUN chip. It’s been my experience that multi-LUN card readers generally present all of their LUNs to the host as soon as it’s plugged in (regardless of whether or not there’s a card plugged into it) — and these readers only present two to my system. (Additionally, the GL3230S is probably more expensive than the GL3231S — and JJS probably wouldn’t have paid extra for those extra LUNs unless they planned to actually use them.)

Based on this, I think it’s probably safe to say that these readers use the GL3231S.

Why all the detective work? Well…if you look at the product page for this reader, there’s a statement that stands out to me. It’s even in the very first paragraph on the page:

Screenshot from Genesys Logic's website, from the product page for the GL3231S.  The statement "GL3231S also supports SANDISK EXTREME 160MB/s microSD UHS-I CARD" is highlighted.

Now…you could make the argument that this statement is only saying that it supports the card itself — not the enhanced transfer rates that this card offers. But if that’s the case, why bother making that statement at all? Without the enhanced transfer rates, the SanDisk Extreme cards are just regular SD cards — and they don’t bother to call out any other SD cards by name. To me, this means that this reader should support the enhanced transfer rates offered by the SanDisk Extreme cards. (I’m also choosing to believe that it supports the SanDisk Extreme PRO cards as well.)

But…the performance measurements tell a different story. Sure, all of the measurements were above average, but were far below the maximum speeds advertised on the package. I was, frankly, disappointed.

Of course…this card reader was able to get higher speeds with the Extreme 32GB — even going well past what SanDisk advertised — so it’s not the card reader that’s the issue here. (I have two additional samples in the package waiting to be tested — perhaps I’ll get better results with those two.)

Now…if we look at it for what it is? Like I said, all performance metrics were above average — with write speeds being more than one standard deviation above average — being beaten out only by one of the Kioxia Exceria G2’s. However, when compared to the other name-brand cards I tested, all performance metrics (with the exception of sequential write speeds) were actually below average. Performance was more than enough to merit the U3 and V30 marks, but — as with the SanDisk Extreme 64GB — random write performance was well short of what would have been needed for even the A1 mark, let alone the A2 mark.

Endurance tests for all three samples are still ongoing:

  • Sample #1’s first error was an eight-sector wide address decoding error during round 2,034; it has survived 2,419 read/write cycles in total so far.
  • Sample #2 has survived 4,707 read/write cycles and also has not experienced any errors yet. As an interesting side note, this card (currently) gets the title of “fastest card during endurance testing”, with an average of about 2.96TiB written to it per day. (I don’t put too much stock in this, however, because most of the cards I’m testing are artificially slowed down during endurance testing due to the fact that the USB bus is almost always being overloaded — and this card is running on a machine where that’s not the case.)
  • Sample #3 has not yet reached the 2,000 read/write cycle mark. It is currently expected to reach this point in July 2024.

June 12, 2024

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