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03-23-2013, 11:57 AM   #1
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USB 3.0 Performance

Looking at the comments on the article The Ultimate Storage Solution? inspired me to do some research into USB3. I was guessing that most of the speed loss (5Gb/s =<bits to byte>> 625MB/s =<8/10 encoding>> 500MB/s) from 500MB/s was due to the device being slow (flash/or the disk controller) but apperently there is issues with the protocol itself.

This article (i do like tomshardware, he has done many good reviews int he past) explains more problems with the protocol. Apparently the USB3 protocol stats that 400MB/s is realistic after more overhead (flow control, link status, framing,...). Then also the data communication protocol (BOT Bulk-only transport). This doesn't allow for command queuing, (think assembly line). There is a new replacement for BOT but it's not widely implements (including no drivers in windows 7) called UAS.


Faster USB 3.0 Performance: Examining UASP And Turbo Mode : USB 3.0: Dude, Where's My Speed?



Anyways i thought it was a good read.

03-23-2013, 12:09 PM   #2
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QuoteOriginally posted by falagund Quote
mments on the article The Ultimate Storage Solution? inspired me to do some research into USB3. I was guessing that most of the speed loss (5Gb/s => 625MB/s =<8/10 encoding>> 500MB/s) from 500MB/s was due to the device being slow (flash/or the disk controller) but apperently there is issues with the protocol itself. This article (i do like tomshardware, he has done many good reviews int he past) explains more problems with the protocol. Apparently the USB3 protocol stats that 400MB/s is realistic after more overhead (flow control, link status, framing,...). Then also the data communication protocol (BOT Bulk-
My rule of thumb is to halve the max theoretical speed and treat that as the best-case speed in practice. And you really need some high-end PC hardware to be able to take advantage of these extreme speeds

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03-23-2013, 12:50 PM   #3
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For networking 100Mb/s i have seen and 11MB download speed (that is as close to the 12.5MB/s theoretical max)
sata2 i have measured speeds of 200MB/s in a PCIexpress x1 (close to 250 theoretical max)
on my 10ks i have measured 107MB/s (close to the 125MB/s spec)

This sort of closeness should be expected from standards.
03-23-2013, 01:03 PM   #4
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So far i know, these speeds are the measured speeds up AND down, so it's actually split.

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