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Helpful answers
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Aug 8, 2015 12:10 PM in response to Michael Flemingby ApMaX,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.
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Dec 11, 2015 12:54 PM in response to ApMaXby ApMaX,Somebody knows if any current Mac has SDXC card slot supporting UHS-II maximum read/write speeds? Thanks.
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Dec 11, 2015 7:56 PM in response to Michael Flemingby Duane,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."
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Dec 12, 2015 12:43 AM in response to Duaneby ApMaX,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.
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Dec 12, 2015 9:31 AM in response to Duaneby ApMaX,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.
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Dec 12, 2015 9:47 AM in response to Duaneby ApMaX,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.
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Dec 12, 2015 10:38 AM in response to ApMaXby Duane,I don't have an iMac with an internal card reader.
I mentioned above ... MacBook Pro Retina 15" mid-2014
If you send me a UHS-II card, I can perform the tests.
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Dec 12, 2015 11:11 AM in response to Duaneby ApMaX,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.
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Dec 12, 2015 12:08 PM in response to ApMaXby Duane,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.
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Dec 12, 2015 12:48 PM in response to Duaneby ApMaX,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?
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Dec 12, 2015 3:06 PM in response to ApMaXby Duane,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.
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Dec 12, 2015 11:57 PM in response to Duaneby ApMaX,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.

