USB 3.1 Gen 1 vs Gen 2 for external drive?

acousticbiker

macrumors 6502
Original poster
Jun 28, 2008
462
6
I have a 1st generation Retina iMac (late 2015) and am using a Samsung T5 250MB hard drive as a boot drive (highly recommended to speed up this otherwise slow computer: https://forums.macrumors.com/threads/upgrading-hard-drive-in-late-2015-4k-imac.2108980/#post-25899165). I notice that it came with a USB 3.1 Gen 1 cable and am wondering whether using a Gen 2 cable would make it any faster.

The product page for the T5 says it’s transfer rate is up to 540 MB/s, so I’m guessing Gen 2 won’t make a difference because Gen 1 would support up to 5 Mbps
 

satinsilverem2

macrumors 6502a
Nov 12, 2013
701
189
Richmond, VA
The cable is not the limiting factor its the interface on the iMac The 2015 iMac only supports USB 3.1 Gen 1 as it was not until 2017 that the iMac added Thunderbolt 3/USB C ports
 

Ledgem

macrumors 68000
Jan 18, 2008
1,751
502
Hawaii, USA
"Otherwise slow computer?" Did you have a model with the Fusion drive, or are you saying that the T5 is much faster than the internal SSD even through USB?
 

jerwin

macrumors 68020
Jun 13, 2015
2,455
4,448
if you follow the first link, you'll discover it's a 4k imac, possibly with a 5400rpm hard drive. No fancy ati graphics card, no skylake cpu.
 

mikehalloran

macrumors 68000
Oct 14, 2018
1,600
390
The Sillie Con Valley
The cable is not the limiting factor its the interface on the iMac The 2015
Correct. The drive is.
Though if you don't have USB 3.1Gen2 ports, the 10 percent improvement won't matter.
There is no 10% or any other difference with a T5. The SATA III SSD inside is the limiting factor, not the bus speed.

Shortly after I got my iMac Pro, I did some bench testing: USB 3; USB 3.1, TB2 Dock via TB3 adapter, TB3 dock (I have at least one of each)... If it's a SATA III SSD, no difference at all.

I used a 50GB file transfer and ran it many times. Something to do one Sunday morning after church.
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if you follow the first link, you'll discover it's a 4k imac, possibly with a 5400rpm hard drive. No fancy ati graphics card, no skylake cpu.
If that's the only drive, you won't be able to repeat my tests. That HDD is a bit slower but not as much as people think.

I bought a USB-C 3.1 external dock and was a little chagrined to find that it was no faster than the USB 3.0 docks I already owned.
 
Last edited:

Fishrrman

macrumors P6
Feb 20, 2009
17,179
5,536
OP wrote:
"I have a 1st generation Retina iMac (late 2015)..."

STOP RIGHT THERE.
You'll see NO benefits from a USB3.1 gen2 drive, because your Mac doesn't support USB3.1 gen2.

You'll get USB3 speeds from the drive...and that's it.

But... one other thought:

If you do get a USB3.1 gen2 drive, you can still use it.
Someday, you're going to get a newer Mac.
And THEN you WILL see the additional speed benefits.
So... if you buy one now, think of it as "planning for the future"...
 

mikehalloran

macrumors 68000
Oct 14, 2018
1,600
390
The Sillie Con Valley
OP wrote:
"I have a 1st generation Retina iMac (late 2015)..."

STOP RIGHT THERE.
You'll see NO benefits from a USB3.1 gen2 drive, because your Mac doesn't support USB3.1 gen2.

You'll get USB3 speeds from the drive...and that's it.

But... one other thought:

If you do get a USB3.1 gen2 drive, you can still use it.
Someday, you're going to get a newer Mac.
And THEN you WILL see the additional speed benefits.
So... if you buy one now, think of it as "planning for the future"...
Only if there’s an NVMe blade or RAID 0,5 or 10 array inside.

A Samsung T5 has a SATA III drive inside. Once again, in case anybody missed it:

There is absolutely no speed difference between USB 3, 3.1 over USB-C, TB 1/2/3, eSATA, 10G Ethernet or any other non-RAID protocol you can come up with. The SATA III SSD is slower than any of them.

If you have a 2017 or later Mac with both ports and a USB-C / USB 3 dock ($39), it’s very easy to do the test. Buy the dock from Amazon so that you can return it when you find no speed difference between it and a @19 USB 3 dock..