I still question if this is a valid use of PCIe x1. Considering the USB 3.0 theoretical maximum is 4.8Gbps and PCIe x1 theoretical maximum is 4.0Gbps; you lose 0.8Gbps of potential speed. That's not a great loss but means you'll never be able to get the maximum performance out of your USB 3.0 devices by using this controller card.
The actual throughput of USB 3.0 is 3.2Gbps (400 megs/sec), well below what is offered by PCIe x1. It's a valid use, and won't cap the performance of a SuperSpeed USB device in any way.
Is the actual throughput for USB 3.0 of 3.2Gbps that you Quote including the protocol overhead? I would expect that like throughput numbers for USB 2.0 it does not. I don't expect that the protocol overhead would take up 1.6Gbps, or even 0.8Gbps, but it will take up a chunk.
I still question if it's the best use when you can get a PCIe x4 controller card with both USB 3.0 and SATA 3.0 that would have no potential bottlenecks. (Asus U3S6 PCIe x4 controller card for SATA 3.0 and USB 3.0)
That number is with protocol overhead taken straight from the USB SuperSpeed whitepapers. The real-world throughput of USB 3.0 will rarely exceed 3.2Gbps.
Let me rephrase, Is the throughput number your quoting from the whitepapers just the throughput, or the total bandwidth used; including both the datarate and the protocol overhead. What I have read leads me to believe 3.2Gbps is just the throughput of the data.
I'm not disagreeing that in the real world that we will rarely see throughput of USB 3.0 data exceed 3.2Gbps. Just like USB 2.0 Theoretical maximum will be much higher then real world application.
Good to know, that the pairing does make sense. At first glance it seems to be a bad pairing, like SATA 3.0 on PCIe x1. Thanks for pulling out the RAW throughput info that really clears things up.
(sorry to get nit picky about it, I just get like that sometimes)
Thrax
🐌Austin, TX Icrontian
Comments
The same thing applies to SATA 3.0 controller cards using PCIe x1. But the loss with SATA 3.0 is much larger.
I still question if it's the best use when you can get a PCIe x4 controller card with both USB 3.0 and SATA 3.0 that would have no potential bottlenecks. (Asus U3S6 PCIe x4 controller card for SATA 3.0 and USB 3.0)
I'm not disagreeing that in the real world that we will rarely see throughput of USB 3.0 data exceed 3.2Gbps. Just like USB 2.0 Theoretical maximum will be much higher then real world application.
(sorry to get nit picky about it, I just get like that sometimes)
??
http://en.wikipedia.org/wiki/PCI_Express#PCI_Express_2.0
PCI-E x1 Gen2 = 5 Gbps / 10 bits per byte = 500 MB/second in each direction
MRFS