Ben is right. The actual limit for a bulk transfer (which is hard drives/printers/scanners etc use) is ~53 MB per second. And this is only if everything goes right (ie there aren't any underutilized frames and everything is on time) and probably requires that you use only 1 endpoint. So actual throughput is going to be much less. R -- You should run usbtree for the drive on both ports (the slow one and the fast one) and see where it ends up. It shouldn't matter where it is plugged in, and if it does it might mean that something is amiss. I think that most USB controllers actualy have control chips for each speed that show up whe you scan the bus. The devices get handed off to the appropriate controller on initial negotiation. A good resource for those interested is: http://www.linux-usb.org/usb2.html you can also get the actual USB 2.0 spec at http://www.usb.org/developers/docs/ but that's heavy boring reading. leif On Wed, 29 Sep 2004 15:21:30 -0500, Ben Neigebauer <ben.neigebauer at compellent.com> wrote: > Actually 16-20 sounds about right from what I have seen. > > There is actually a lot of CPU work for USB (that's why intel pushes it) > > In my informal testing, FireWire has faster transfers and lower CPU when > you use a decent FireWire card. > > Don't be fooled by the 480 vs. 400 numbers, a lot of it's taken up by > overhead. > > > > > -----Original Message----- > From: tclug-list-bounces at mn-linux.org > [mailto:tclug-list-bounces at mn-linux.org] On Behalf Of Florin Iucha > Sent: Wednesday, September 29, 2004 3:04 PM > To: Leif Johnson; TCLUG Mailing List > Subject: Re: [TCLUG] USB hard drives > > On Wed, Sep 29, 2004 at 01:38:08PM -0500, Leif Johnson wrote: > > I wouldn't expect the same latency or transfer rate from a USB drive > > as an IDE one. I haven't actually done the math, but I don't think > > that the bus can support it. > > USB 2.0 "480 MBs". I would expect a sustained throughput of 35-40 MB > or so, without much CPU usage. I get around 16-20 and the CPU is > working hard (it's a PII/450). > > > Your latency and throughput will also > > depend on what other devices you have plugged into that controller, > > and the host/os implementation. > > Nothing. Linux. 2.6.7. > > > What filesystem is on the hard drive? > > ext2 > > florin > > -- > > Don't question authority: they don't know either! > > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > Help beta test TCLUG's potential new home: http://plone.mn-linux.org > Got pictures for TCLUG? Beta test http://plone.mn-linux.org/gallery > tclug-list at mn-linux.org > https://mailman.real-time.com/mailman/listinfo/tclug-list > _______________________________________________ TCLUG Mailing List - Minneapolis/St. Paul, Minnesota Help beta test TCLUG's potential new home: http://plone.mn-linux.org Got pictures for TCLUG? Beta test http://plone.mn-linux.org/gallery tclug-list at mn-linux.org https://mailman.real-time.com/mailman/listinfo/tclug-list