Date: Tue, 18 Jan 2000 10:50:19 +0000 (GMT) From: Nick Hibma <n_hibma@webweaving.org> To: Alex Zepeda <jazepeda@pacbell.net> Cc: Bill Paul <wpaul@skynet.ctr.columbia.edu>, current <current@FreeBSD.ORG> Subject: Re: USB D-Link DSB-650 kue0: failed to load code Message-ID: <Pine.BSF.4.20.0001181045440.725-100000@localhost> In-Reply-To: <Pine.BSF.4.21.0001171602590.1791-100000@localhost>
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Both are specifications for USB Host controllers. The difference between them is internals of the chip and the interface exposed on the PCI bus. In brief: OHCI is made by M$ and emphasizes the fact that hardware should be smart to facilitate the software's task. UHCI is made by Intel and stupid, in order to facilitate a low gate count. Bottom line, OHCI has some brains and is actually able to transfer 8kb transfers in one go. UHCI needs to be told _every_sinle_thing_ about a transfer: transfer descriptors, size of transfers, but also the sequence in which iso, interrupt, bulk and control transfers need to be done. Also the number of interrupts is large, and when an interrupt happens you'll have to search for the transfer that created the interrupt. Overhead on the PCI bus should be lower for OHCI as the controller only has to fetch the description for the transfer once and then can transfer up to 1kb on the bus in one go. OHCI is being used in firewire as well I believe. UHCI will not be able to support those speeds (nor will it support USB2.0 without some change of the specification) Both host controllers will support all the USB devices and there should be no difference in using either of them. There will be some devices that are supported by one or the other, but those devices are probably old (some Genius mice come to mind) and newer devices should not have those problems. In FreeBSD the problem is that UHCI is slightly better supported than OHCI. isochronous transport does not work yet with OHCI. Also, I have been too lazy (busy?) to fix a few major issues with ohci and recognising devices. Apologies for that, but no one was willing to pay me for doing the open source FreeBSD USB stuff (until now) and time was limited due to some external factors. Hope this explains a bit. Nick On Mon, 17 Jan 2000, Alex Zepeda wrote: > On Mon, 17 Jan 2000, Bill Paul wrote: > > > I also noticed that performance with the OHCI controller is significantly > > better than with the UHCI controller. Just my rotten luck I'm stuck > > with a UHCI one in my laptop. > > Ok, with all this flurry of USB development, I keep seeing UHCI and > OHCI. What's the difference? > > - alex who thought USB ethernet was bad until he had to buy an AAUI transciever > .. > builtin ethernet my ass > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-current" in the body of the message > -- n_hibma@webweaving.org n_hibma@freebsd.org USB project http://www.etla.net/~n_hibma/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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