Late 2015 iMac. Fastest Data Transfer from new USB-C devices

Hello, Thank you if you can help...


After much researching, I still cannot establish which is the fastest port on my iMAC AND from which there is an adaptor to accept new USB-C devices.


For some reason the vast majority of adapters are the wrong way round, ie, they will connect multiple connector types, female, to USB-C, male, but not vice-versa. ... as if they cater for connecting old devices to new computers, and not old computers to new devices!


... any suggestions please...?


TIA.




iMac 27″, macOS 10.13

Posted on Sep 7, 2023 4:09 AM

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Question marked as Best answer

Use USB-C to USB-A adapters in the iMac's USB 3 ports.



have a look at > usb-c to usb-a adapters

Posted on Sep 7, 2023 5:18 AM

22 replies

Sep 7, 2023 8:28 AM in response to Martin-123

My real world experience on that very model is the USB-3 ports are running at 559 MB/s this very moment and the Thunderbolt 2 ports are a dead issue.


The port controls the speed regardless of adapters used. The same is true on our 2020 27" iMacs ... USB 3 559 mB/s. The USB-C ports allow about 1030MB/s.


These are speeds associated with Samsung T7 SSDs which have a Mac advertised speed of 1050MB/s

Question marked as Helpful

Sep 7, 2023 8:58 AM in response to Martin-123

Why disappointing? 559 MB/s is very good for an old soon-to-be obsolete device. When I was booting from an external T7 drive, the machine was a pleasure to use. You have to accept limitations, and this is it for that model.


TB2 is just not a viable option. I found some equipment that was advertised to work in 2020, but at 5x the cost of a USB-A device it was not practical. The cables themselves can run $50US and you have to make sure you steer clear of Display Port cables as they have the same connectors. OWC used to sell TB2 gear, but a search of their site returns nothing today.


If you can find the gear and are willing to pay the price, then by all means do so.

Sep 7, 2023 1:38 PM in response to Martin-123

Re: “Thunderbolt 2, "a dead issue" “


Thunderbolt 1 & 2 use the Mini DisplayPort connector. Seeing the work on USB-C, Intel decided that Thunderbolt would gain more traction by becoming an ALT mode on USB-C than by staying on the Mini DisplayPort connector.


So you need a $50 adapter to go between TB 3 or 4, and TB 1 or 2. That adapter does not carry power, so you cannot use it to plug a bus-powered TB 3 SSD directly into a TB 2 equipped Mac.

Late 2015 iMac. Fastest Data Transfer from new USB-C devices

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