Messages in this thread |  | | Date | Sat, 28 Jun 2003 20:34:17 -0700 | From | David Brownell <> | Subject | Re: bkbits.net is down |
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> From: Alan Cox > Date: 2003-06-28 23:13:55 > > On Sad, 2003-06-28 at 23:15, Dr. David Alan Gilbert wrote: > > Hmm - why should it suck so badly? Shouldn't USB 2 (yes I mean the > > 480Mbps) manage 40MByte/s+ ?
Custom devices certainly have done that, with drivers that keep everything busy. Last fall, one person reported 38+ MB/sec from a VT8235. The theoretical peak bandwidth for bulk traffic (what most folk want) is 52 MByte/sec.
A Western Digital drive I tried gave me 27 MByte/sec with USB. And I hate to say that the FireWire mode didn't work at all, since I was curious how they'd compare! (2.5.71 or so.)
> I don't think you get the full 480Mbit/sec on a single device. > 5Mbyte/sec is a bit low
Some combinations of EHCI silicon, USB-to-IDE adapter, and IDE work better than others ... I once switched a drive from one EHCI controller to another (same host and OS, didn't reboot), and went from 5 MB/s to 19 MB/sec. That was on 2.4; with the 2.5 usb-storage, both controllers gave the higher speed.
> but that may be some of the remaining work on > the USB EHCI drivers. I've not tried 2.5.x which may be way better here.
The key difference in 2.5 is that usb-storage queues requests, no more slow page-at-a-time I/O. It's the same EHCI driver underneath, lately -- much improved since last September (or so) when it first started to generate real user feedback.
- Dave
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