SDXC slot compatibility

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 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.

Well, that is interesting. Then, it seems that laptops and desktops have different internal wiring for the built-in card readers.

In any case, I have found that the Apple specifications are wrong, at least for the Mac mini and iMac described above. They show 2.5 GT/s" (250 MB/s), yet they only have 100 MB/s in real-life tests with UHS-II cards.

Which model/year is your MacBook Pro?

Could you do some real tests of write/read speeds with UHS-II cards in your MacBook Pro? You can use QuickBench of DiskTools Pro (commercial), or the free Disk Speed Test (BlackMagic). Thanks.

I'm not sure where you are getting your information. The links you provide do not say anything about testing with a Mac.

The system information you posted does not match the information found on my MacBook Pro Retina 15" mid-2014

Nope. What I posted is showing the connection to the internal card reader in my MacBook Pro.

The card reader does not show up under Hardware -> Card Reader.

And yes the card reader works just fine.

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.

You said "Well, that is interesting. Then, it seems that laptops and desktops have different internal wiring for the built-in card readers."

I replied "I don't have an iMac with an internal card reader."

You said "Which model/year is your MacBook Pro?"

I replied "I mentioned above ... MacBook Pro Retina 15" mid-2014"

You said "Could you do some real tests of write/read speeds with UHS-II cards in your MacBook Pro? "

I replied "If you send me a UHS-II card, I can perform the tests."

The OP's original question -> Will the SDXC slot on a 2015 MacBook Pro 13inch read the latest UHS-II SD memory cards at 150MB/s or 300MB/s?

I replied 'According to About the SD and SDXC card slot - Apple Support, "Mac notebooks use the USB bus to communicate with the SD card slot and have a maximum speed of up to 480 Mbit/s."'

- 480 Mbit/s is 60 MB(yte)/s [assuming 8 bits per Byte]

- So the answer to OP's question is no. The SDXC slot on the new MacBook Pro can not read the cards at 150 MB/s or 300 MB/s.

According to About the SD and SDXC card slot - Apple Support, "Mac notebooks use the USB bus to communicate with the SD card slot and have a maximum speed of up to 480 Mbit/s."

Somebody knows if any current Mac has SDXC card slot supporting UHS-II maximum read/write speeds? Thanks.

Besides such STANDARD "Bus Speed"

https://www.sdcard.org/consumers/speed/bus_speed/index.html

is there any Mac supporting also the known as MAXIMUM SPEED?

https://www.sdcard.org/consumers/speed/max_speed/index.html

Examples of Maximum speeds for UHS-II cards:

Lexar 64GB Professional 2000x UHS-II U3 SDXC (300 MB/s read & 260 MB/s write)

http://www.lexar.com/pro-2000x-sd?category=5286

SanDisk 64GB ExtremePRO UHS-II SDXC Memory Card (280 MB/s read and 250 MB/s write)

http://www.sandisk.com/products/memory-cards/sd/extremepro-sdxc-sdhc-uhs-ii/?cap acity=64GB

Thanks.

Yes, I kow, but that is simply not true. For insance, the iMac or Mac mini (late 2012) SDXC reader is compatible with UHS-II cards (reads/writes them), but at UHS-I speeds (100 Mbps) instead of UHS-II speeds (300 Mbps). Tested in the real-world with UHS-II cards, which have an extra row of contacts (pins) as shown at

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

https://www.pretzellogix.net/2014/10/24/a-list-of-all-uhs-ii-sd-cards-readers-an d-cameras/

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

Even more, the "Apple - About This Mac - System Reports - Hardware - Card Reader" on such Macs shows "Link Speed: 2.5 GT/s" (250 MB/s), which again is not true. That may be the bus speed, but the Apple SDXC readers in such Mac models do not have the pins to support it, since they do not deliver UHS-II speeds but lower UHS-I speeds.

In summary, the Mac motherboards and port buses may support such UHS-II speeds, but the built-in Apple Mac SDXC readers must have such extra pins, or else will read UHS-II cards with UHS-II speeds.

Somebody knows if any current Mac has SDXC card slot supporting UHS-II maximum read/write speeds? Thanks.

Thanks, but that is not what I meant:

I said:

"Apple - About This Mac - System Reports - Hardware - Card Reader"

But you have posted a different component:

"Apple - About This Mac - System Reports - Hardware - USB"

The former is the Apple Mac built-in SDXC Card Reader, which is what I asked for. The latter is an EXTERNAL card reader connected to a Mac USB port. It is not the same.

I did the testing myself with Mac mini and iMac as described above. So, the question remains:

Somebody knows if any current Mac has SDXC card slot supporting UHS-II maximum read/write speeds? Thanks.

Thanks. You said:

- What I posted is showing the connection to the internal card reader in my MacBook Pro.

- I don't have an iMac with an internal card reader.

But the Mac model is irrelevant. What I asked for is if somebody could check if any Mac can actually read/write UHS-II cards with 300 Mbps speeds in real-world tests.

I do not have UHS-II cards. I tested one before purchase and got the shocking results described above (100 Mbps read/write instead of 300 Mbps). And now I am looking for new Mac models that may have true UHS-II card readers to purchase them. Thus, my question.

Thanks. Such Apple specification should be wrong again. I am sure your MacBook Pro Retina 15" mid-2014 should read at least at UHS-I speeds (100 MB/s), if not UHS-II, because much older Macs do read/write at such UHS-I speed. Clearly, Apple got it all wrong in these specifications. That is why real-world tests are needed. Anyone can do such tests?

No, they are not correct. 60 MB/s are not 100 MB/s. In fact, 104 MB/s:

Bus Speed

https://www.sdcard.org/consumers/speed/bus_speed/index.html

And as said this is also wrong:

About the SD and SDXC card slot

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

Mac notebooks use the USB bus to communicate with the SD card slot and have a maximum speed of up to 480 Mbit/s. Mac desktops use the PCIe bus to communicate with the SD card slot and can transfer data at a 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.

All explained above. Again, real-world tests are needed to truly determine the real read/write speeds.