Q: SDXC slot compatibility

I'm having a hard time with your posts since you seem to hop here and there and apparently contradict things that you have said.

You said that you had tested and found that the Mac support 100 MB/s.

Apple specs say that they support up to 60 MB/s.

You claim that Apple's specs are not correct. It appears that your tests show that the Mac performs better than Apple's specs. So the Apple specs are not wrong since they meet 60 MB/s... they just understate the capability. Apple's specs do not claim to support the highest speeds capable of the UHS-I and UHS-II devices. I never said that they did.

You now claim that 60 MB/s is 104 MB/s. It is not. I never said that 60 MB/s is 100 MB/s. 60 MB/s is 60 MB/s.

It is quite simple indeed:

1. In the Mac mini and iMac previously indicated, "Apple - About This Mac - System Reports - Hardware - Card Reader" shows "Link Speed: 2.5 GT/s" (250 MB/s). That is not true.

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

About the SD and SDXC card slot - Apple Support

it says Mac desktops use the PCIe bus to communicate with the SD card slot and can transfer data at a faster rate.

Select Card Reader from the Hardware section (for Macs that use the PCIe bus to communicate with the SD card slot). Look for the Link Speed entry. Computers that use the PCIe bus express their speed as GT/s.

That is not true again.

They are not true because UHS-II cards with 300 MB/s only have real-test speeds of 100 MB/s in such Macs which should have 250 MB/s.

So, again, real-world tests are needed to truly determine the real read/write speeds. Somebody knows if any current Mac has SDXC card slot supporting UHS-II maximum read/write speeds in real-world tests? Thanks.

Hi ApMaX

I Tested Lexar Professional 1000x in my iMAC mid 2011, but I just got 11 MB/s (Write) and 21.4 MB/s (READ).

I'm going to try this post

http://apple.stackexchange.com/questions/56159/how-can-i-speed-up-sd-card-writin g-speed-using-dev-disk-on-a-macbook-pro

Duane wrote:

 

The Apple specs that I linked to indicate 60 MB/s and you state that you have tested to 100 MB/s so it would seem that the Apple specs are correct.

Duane you have the patience of a Saint !  I would give you points for that alone.

p.s. It would be nice to hear back from the OP !

It is a hardware issue:

A list of UHS-II SD cards, readers, and cameras

https://www.pretzellogix.net/wp-content/uploads/2014/10/uhs-i-vs-uhs-ii.png

.

I know this thread is old, but it got bumped, and I found it looking for the same answers.

Having done some research, I understand the following:

The MacBook Pro over time has various SD cards readers installed.  The support article specifies that the laptops only connect via USB 2.0 @ 480Mb/s, but I think that is worst case scenario.  I have a MacBook Pro 2012 13" that reports its SD Card reader as on the PCIe bus, so that's 250MB/s.  I also have MacBook Pro 2015 13" that reports the card reader on the USB 3.0 bus at 5.0GB/s.  Nice.

However, UHS-I has a maximum speed of 50MB/s which was later uprated to 104MB/s by mandatory overclocking of the signal bus.  I have access to a SanDisk Extreme Micro SDXC UHS-1 U3 card which writes happily at 50MB/s and reads at 75MB/s in both the 2012 and 2015 MacBook Pros.  I conclude, therefore, that MacBook Pros shipping from 2012 onwards (perhaps earlier) support UHS-I transfer rates.

It is, I think, quite clear that no current Apple product is shipping with support for UHS-II, which requires an additional row of hardware pins to support the double channel data speeds required by UHS-II.  However, external readers via USB 3.0/3.1 would achieve those speeds without issue.

Hope that helps.

Steve.

"It is, I think, quite clear that no current Apple product is shipping with support for UHS-II, which requires an additional row of hardware pins to support the double channel data speeds required by UHS-II."

Maybe, or maybe not. That is why I asked for real-world testing? Someone has latest Mac and can UHS-II reader to see real read/write speeds?

ApMaX wrote:

 

 

Maybe, or maybe not. That is why I asked for real-world testing? Someone has latest Mac and can UHS-II reader to see real read/write speeds?

And I have done.  The real world test, I did, in the post above, which clearly shows that both MacBook Pro 2012 13" and Macbook Pro 2015 13" support UHS-I speeds.  They can't support UHS-II as they don't have enough pins in the card reader. If you still don't believe me, have a look inside your SD Card reader, you'll see a row of contacts at the back and 4 brushes/grips in front of them.  You need a second row of contacts to support UHS-II.

Let me add something to this discussion: I have just glimpsed into the SD slot of my Late 2013 MacBook Retina 13" and it seems to me that there is very little space left for those extra row of contacts. The card reaches about 16mm into the side of the notebook, minus 2mm for the aluminium shell. If I read the above image correctly, the UHS-II pins end at about 11mm, which gives us just 3mm space between the reader pins and the outer shell.

Maybe not worth the trouble from Apple's point of view?