Apple has now confirmed the specifications for the built-in SD card slot on the new MacBook Pro. Disappointingly, the speed will max out at a little over 300MB/s.
Apple confirmed the speed to The Verge’s Dan Seifert, who posted the information to Twitter. Further, 9to5Mac shared an excellent breakdown of the various SD card standards, since it can be rather confusing.
First, there are two physical sizes of SD card — ‘full size’ SD cards and microSD cards, which are much smaller. You can get adapters to use microSD cards in full size SD card readers, however.
Apple has confirmed to us that the SD card slot in the new MacBook Pro 14/16 is UHS-II (over 300Mbps). Not as forward looking as UHS-III (over 600Mbps) would be, but thank god it's not UHS-I (about 100Mbps) . https://t.co/MN1ZCLyC4T
— dan-dor the relentless (@dcseifert) October 19, 2021
Next up are capacity categories, all of which the new MacBook Pros support:
- SD (up to 2GB)
- SDHC (up to 32GB)
- SDXC (up to 2TB)
- SDUC (up to 128TB)
Finally, are the speed ratings. We marked the ones supported by the new MacBook Pros with an asterisk (*) below:
- Standard SD* – 12.5MB/s
- High Speed (HS)* – 25MB/s
- Ultra High Speed I (UHS-I)* – 104MB/s
- Ultra High Speed II (UHS-II)* – 312MB/s
- Ultra High Speed III (UHS-III) – 624MB/s
- SD Express (HC/XC/UC) – 985MB/s or 1,970MB/s or 3,940MB/s
To further complicate all this, some UHS SD cards will show half of the speeds listed above. This is because that’s the maximum full ‘duplex speed’ where one lane each is assigned to a “downstream direction” like transferring data from the host to a card, and the other assigned to “upstream” for transferring data from the card to a host. Cards can also operate in a “half duplex” mode and use both lanes for one direction. According to the SD Association’s website, a UHS-II card could operate at 156MB/s in full duplex or 312MB/s in half duplex.
While it’s great that the new MacBook Pros brought back the SD card slot, it’s a little disappointing that it doesn’t support higher speeds. For most use cases, UHS-II is likely fine. But professional users like videographers or photographers may find themselves bumping up against that transfer speed ceiling more often than not.