2013 MBA and SD Card Reader

What is the maximum speed that my computer can use when reading and writing to an SD card in the SD card slot?

Macs that use the USB bus to communicate with the SD card slot have a maximum speed of up to 480 Mbit/s. Newer Macs use the PCIe bus to communicate with the SD card slot and can transfer data at a much faster rate.

Check the packaging that came with your SD media to determine the maximum transfer rate used by that specific card.

Determine the maximum speed of your Mac using the System Profiler:

1. Choose About this Mac from the Apple () menu.
2. Click More Info.
   1. Select USB from the hardware section (for Macs that use the USB bus to communicate with the SD card slot).
   2. Select Internal Memory Card Reader and look for the Speed entry.
   or
   1. Select Card Reader from the Hardware section (for Macs that use the PCIe bus to communicate with the SD card slot).
   2. Look for the Link Speed entry. Computers that use the PCIe bus express their speed as GT/s.

youre also trying to write to a micro SD card thru a SD to micro caddy.

There's some inconsistency from Apple on whether the SD slot is connected via USB bus or PCI-E bus. The SD article from Apple mentions "newer Macs" as connecting via PCI-E, but System Profiler doesn't agree, showing it connected to the USB 3.0 bus on the 2013 MBA (my 2012 MBA shows the SD slot as connected to a USB 2.0 bus with max speed of 480 Mb/s).

Also the 5Gb/s speed you're seeing for the SD slot is 5 gigaBITS per second, so divide that by 8 to get gigabytes per second (640 MB/s).

Plot -- the microSD adapter does not affect speed since it's a passive adapter.. It just connects the pins together.

SD Card Readers in the current MacBook Pros are connected via pcie NOT however the current 2013 Air

You got the other info off Apple which states: Macs that use the USB bus to communicate with the SD card slot have a maximum speed of up to 480 Mbit/s. Newer Macs use the PCIe bus to communicate with the SD card slot and can transfer data at a much faster rate.

Im also quite sure the OP was not using a FAST microSD card,....last I recall you cant even find FAST microSD in retail electronics.

Determine the maximum speed of your Mac using the System Profiler:

1. Choose About this Mac from the Apple () menu.
2. Click More Info.
   1. Select USB from the hardware section (for Macs that use the USB bus to communicate with the SD card slot).
   2. Select Internal Memory Card Reader and look for the Speed entry.
   or
3. Select Card Reader from the Hardware section (for Macs that use the PCIe bus to communicate with the SD card slot).
4. Look for the Link Speed entry. Computers that use the PCIe bus express their speed as GT/s.

Class 10 cards should get transfer speeds of at least 10MB/second, while cheaper microSD cards have as low as 4MB/second transfer speeds. Transfer speeds will also depend on the mac as older MacBooks treat the SD card slot as a USB 2.0 connection, while newer ones use the PCIe bus to connect to the SD card slot.

real-life testing gets about 10MB/second transfer speeds. Copying a ~600Mb file took right around one minute. That’s slower than transferring to USB 3 external hard drive (copying the same file took around 40 seconds)

Thanks for the reply. I'm going to guess that the Apple article (http://support.apple.com/kb/HT3553#4) lists "new Macs" as using the PCI-E bus when they should've specified "new MacBook Pros" and maybe iMacs. I haven't been able to find any definitive source though that says that the Macbook Air SD card reader uses USB, while the Pro uses PCI-E.

What I did find:

• 2013 Macbook Air - shows SD card slot connected to USB 3.0 bus in System Profiler
• 2012 Macbook Air - shows SD card slot connected to USB 2.0 bus in System Profiler
• 2012 Macbook Air SD card performance appears to be capped at 40MB/s. This would make sense then that the SD card is connected to a USB 2.0 bus indeed (http://www.anandtech.com/show/6063/macbook-air-13inch-mid-2012-review/2).
• 2012 Retina Macbook Pro - 80MB/s using UHS-1 SD card (http://www.anandtech.com/show/6023/the-nextgen-macbook-pro-with-retina-display-r eview/13).

If you can find any source that says that the Macbook Air uses USB and Macbook Pro uses PCI-E, could you please link?

"Newer Macs use the PCIe bus" is off Apples own site. however this generalization doesnt seem to cover the Air specifically as per the 2013, unless info to the contrary (which I can find nowhere, not even on my own 2013 AIR) pops up.

http://support.apple.com/kb/ht2838

http://support.apple.com/kb/HT3553

😊

Simply for information: My New Macbook Pro Retina (Currently shipping model, FULLY upgraded) 13.3" shows the card reader as being slaved to the USB 3 BUS with a 5GB/sec transfer rate.

I am wondering if the Macbooks apply or if it's a 15" retina feature only in the Macbook line. Considering the focus on PCIe interconnect, I am unsurprised that the PRO would use a PCIe bridge to card slot.

Titania1160 wrote:

Simply for information: My New Macbook Pro Retina (Currently shipping model, FULLY upgraded) 13.3" shows the card reader as being slaved to the USB 3 BUS with a 5GB/sec transfer rate.

I am wondering if the Macbooks apply or if it's a 15" retina feature only in the Macbook line. Considering the focus on PCIe interconnect, I am unsurprised that the PRO would use a PCIe bridge to card slot.

You'll be surprised to know that my Late-2013 Macbook Pro Retina 15inch has the same specs for the SDXC card. My system information has the it rated at 5Gb/s linked through USB 3.0 SuperSpeed bus.

Scott

Hi Josh

I got a MBA from 2013.

I have bought a Nifty Drive and start testing the best microSD to fit there. I bought a ScanDisk Extreme Micro SDXS 64 GB with a transfer rate up to 80 MB (90€), it works nicely but with a max transfer rate of 33 MB r/w but I don't understand, why it does not reach even the USB 2.0 480 Mb (60 MB) which apple announce on their support page. From my point of view it could be the SD card, as I got with other cards better performance at least on Read (using for test the BlackMagic from app store).

Therefore the key point here could be..... Which Micro SD or SD card it is better for our MBA to get better I/O rates.

The maximum speed is the lowest between the bus and the reader. The bus may be great, but if the reader does not deliver, the latter is the maximum speed. Someone has real-world tests?

Wow, Oct. 12, 2015 and still helping with your post (MacBook Pro 9,2). Thanks much...

Yeah, for at least my 2012 13" MBP (9,2) here's the "About this Mac/More Info/System report" page...

There's a Sandisk Extreme Pro micro-SD card loaded with specs of 95MB/s read and 90MB/s write; these are the specs I got (thru a SD card caddy) with the AJA test...

Well within USB 3.0 delivery (conceivably @671MB/s). So moot point due to card speed, so far. I dream of card speed pushing even USB 3.0, much less 3.1 (10Gb/s, finally equal to 1st generation Thunderbolt). Some overhead left in the little cards, real recorders use 2.5" SSDs for serious speed (500MB/s+)...

Thanks. It would be great if someone could test SDXC/SDHC UHS-II cards like the ones of Lexar or SanDisk (specifications of about 300 MB/s read/write) using the Mac built-in SDXC readers.