Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Morien

macrumors member
Original poster
Oct 25, 2010
68
6
Hi,

How do USB 2.0 devices (specifically hdds) perform through a USB 3.0 hub? Do they go full speed (when both being accessed at the same time) with the extra Usb3 overhead? Or does it perform the same as a usb2 hub? (with both devices competing for bandwidth)?

Also, I have noticed that some hubs have USB 3.0 specific ports, along with USB 2.0 specific ports. The hubs I have found near me for sale though just have USB 3.0. I have heard that plugging a usb2 device in along with a usb3 will slow down all devices to usb2 speeds. Is this true?

Thanks
 

Comeagain?

macrumors 68020
Feb 17, 2011
2,190
46
Spokane, WA
Any device will "max out" at the slowest piece of the signal chain. Ie, a USB 2.0 external drive will be that same speed whether using USB 2 or 3, even going through Thunderbolt, it will always be USB 2 speed.
 

Morien

macrumors member
Original poster
Oct 25, 2010
68
6
Hey comeagain,
I know that I won't experience any increase in speed, but what I'm asking is if I would experience a slowdown comparable to if two drives were connected to a usb2 hub and accessed at the same time (for simplicity sake, we'll just assume that the bandwidth of the usb2 hub is evenly halved, causing both devices to go at half speed).

So, since USB3 supports a speed of up to 625MB/s max, would two usb2 drives (60MB/s max theoretically) be able to transfer data simulateousoy at their max speed (a combined 120MB/s)? Or would they act as if they are both connected to a USB2 hub (a combined 60MB/s, or 30MB/s each)?

Thanks a lot
 

theSeb

macrumors 604
Aug 10, 2010
7,466
1,893
none
Hey comeagain,
I know that I won't experience any increase in speed, but what I'm asking is if I would experience a slowdown comparable to if two drives were connected to a usb2 hub and accessed at the same time (for simplicity sake, we'll just assume that the bandwidth of the usb2 hub is evenly halved, causing both devices to go at half speed).

So, since USB3 supports a speed of up to 625MB/s max, would two usb2 drives (60MB/s max theoretically) be able to transfer data simulateousoy at their max speed (a combined 120MB/s)? Or would they act as if they are both connected to a USB2 hub (a combined 60MB/s, or 30MB/s each)?

Thanks a lot
Real world USB 2.0 performance is around 25-30 MB/s, not 60 MB/s. Whether you get half the bandwidth or not when using a hub depends entirely on the hub. With a USB 3 hub, you would get your maximum USB 2 performance for each USB 2 device that is connected. Unless you bought it for $5.
 

Morien

macrumors member
Original poster
Oct 25, 2010
68
6
Hey theseb,

I know that real world speeds are lower, but you've answered my question. Thanks
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.