Quick Review: Samsung Pro 32Gb UHS-I microSDHC Card

UPDATED: Compatibility with RTS5301 workaround found!

Merely a few days ago, I reviewed the Samsung Plus 32Gb UHS-I microSDHC Card and wondered exactly how the Pro performs in comparison – what are you really missing out on? As a result, I went a little crazy and started ordering quite a few 32Gb microSDHC cards for comparison testing – after all, I’ll find a use for them someday, right?

That aside, I purchased this card from an Australian source on eBay, for a cost of AU$38. It’s roughly AU$9 more than the Samsung Plus, but it promises up to 70Mb/s as opposed to 48Mb/s as for the Plus. It also quotes a write speed of up to 20Mb/s, whereas none was written on the packaging of the Plus.

DSC_8600 DSC_8601

The card itself is model MB-MGBGB/CN, indicating it is for the Chinese market and contains both English and Chinese text on the rear. Interestingly, the conditions for the warranty are clearly stating to exclude write-heavy loads.

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The card itself looks consistent with the Plus, in true Samsung style. No adapter was provided with this one, as expected.

The particulars of the card is as follows:

Size: 32,093,765,632 bytes
CID: 1b534d3030303030103be1772900d173
CSD: 400e00325b590000ef1d7f800a400027

Interestingly, compared to the Plus, this card has exactly 623MiB more room! That’s more than half a gigabyte of real capacity difference. At least this one actually provides at least 32Gb (weasel gigabytes).

Performance Testing

The card was run through the full-random fill and three pass verify with no dramas at all.

Sequential Read – HDTune with Transcend RDF8


Testing with the Transcend RDF8 resulted in a result which was below the 70Mb/s stated, but did approach it with an average of 58.9Mb/s. Interestingly the transfer rate has a stepped appearance which alludes to the different flash dies used internally – they may have different read-speeds and latencies! Or maybe it’s an illustration of how the card’s performance timing interacts with the Genesys Logic chipset in this reader. How unusual!

Sequential Read – HDTune with Kogan RTS5301


Testing sequential read with HDTune unveiled a compatibility issue with the Samsung Pro and the Kogan RTS5301 reader where UHS-I mode was not active, instead, the card operated in the normal SD 4-bit mode (25Mhz * 4 bits * DDR = 25MB/s = 23.84MiB/s speed maximum). Unfortunately, multiple plug and unplug operations could not resolve this – it may be a firmware bug with the RTS5301 or a problem with some of the manufacturer register data in the microSD card.

UPDATED: Sequential Read – HDTune with Kogan RTS5301


As I ended up discovering, if the microSD card is thrown into an adapter to turn it into a full-size SD card, and plugged into the corresponding slot of the RTS5301, it negotiates and runs in UHS-I mode correctly. It’s probably a card reader peculiarity. It’s faster than the RDF8 and doesn’t have any of the bumpiness.

After performing that operation, plugging the card back into the microSD slot resulted in no UHS-I performance until it was slipped into an adapter again!

CrystalDiskMark – Transcend RDF8


Testing with CrystalDiskMark showed the sequential read rate to barely exceed the 70Mb/s stated on the package. The write speed exceeded the 20Mb/s on the package as well, however, comparing with the Plus’ result of 44.31Mb/s and 27.95Mb/s respectively, it seems that the higher read speed comes at a cost of write speed. This is especially noticeable in the smaller block write performance where the Plus turned in 23.11Mb/s for 512kB and 1.897Mb/s for 4k, both of which are better than the Pro.

CrystalDiskMark – Kogan RTS5301


The Kogan RTS5301 maintains its stubborn refusal to co-operate in UHS-I mode, and as a result, displays a lower performance. Again, the RDF8 seems to be the preferred reader.

UPDATED: CrystalDiskMark – Kogan RTS5301


Using the workaround described earlier, this is the performance the RTS5301 can extract from the card. Curiously, while the reader gets a good score with HDTune, the speed from CrystalDiskMark is a bit lower.


Samsung seems to have done another good job with the Pro, achieving high read speeds at a reasonable price unlike their main competitors. Unfortunately, it seems to come at the cost of the roundedness of the card in small block performance, and where ultimate read performance isn’t the aim – the Samsung Plus is both cheaper and more well rounded for a mixture of reads and writes. By no means is the Pro a bad card, but the Plus seems to be more alluring for me … personally … and the compatibility problems with the RTS5301 may allude to further compatibility issues with other devices as well. Or it probably alludes to problems with the RTS5301 chipset altogether!

About lui_gough

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