Date: Sun, 31 Jan 1999 00:06:47 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: dot@dotat.at (Tony Finch) Cc: hackers@FreeBSD.ORG Subject: Re: USB drivers Message-ID: <199901310006.RAA25943@usr04.primenet.com> In-Reply-To: <E106FOS-0003F1-00@fanf.noc.demon.net> from "Tony Finch" at Jan 29, 99 02:59:36 pm
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> >Anyone considered building a PC whose only means of talking to > >the world is a USB port? > > It'd be rather crippled with only 12Mbit/s of IO. Beats ethernet... > >Anyway, Amancio says he'd prefer FireWire for the monitor (at it's > >slowest, FW can transfer 68 Mbits/S more a second than PCI!), but > >of course he's a video geek. 8-). > > I think you have your bits and bytes mixed up :-) Firewire starts out > at 100Mbit/s (or at least it did when I first heard about it in 1994) > and PCI starts at 132Mbyte/s. IIRC Firewire was designed to be > extended to 800Mbit/s which doesn't get very near PCI's minimum. Feh. You're right. Mea Culpa (and the maximum is 400Mbits/S). On the plus side, the PCI number you have is a burst rate, and not sustainable for something like a video frame rate. > For good video you need 3Gbit/s to the tube (1600*1200, 72Hz, 24 bpp). That's assuming you are drawing the raster line over the serial wire. What you should do instead is send S3/ATI/whatever commands to a chipset in the monitor case, running the raster out of dual ported RAM based on what the engine has been told to render. This is less useful for, say, throwing BT848 input to a monitor, but you'd expect that video hardware would use the computer as a peripheral instead of the other way around (i.e., you're video-in-to-video-out would ignore the computer, for the most part, if you are trying to move all of the pixels in sync with an input source, as opposed to generating the pixels computationally. > >So maybe a box with just a power connector, a FW port and a USB hub > >chip (to seperate the "A" and "B" devices). > > That would be cool. And I guess the ability to pull an Amiga and use a section of main memory as video memory, with a memory bus connector, instead of on-board video hardware. Too bad about the video bandwidth requirements that the gamers are forcing onto us server geeks... 8-(. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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