[linux-audio-dev] Fwd: OT -- USB History

Hi all, sorry for cross posting, but I found the following info very interesting when discussing about USB 1.1 vs. USB 2.0 stuff. Some of us (including me) would like to see a USB 2.0 breakout box which grants more than 2x2 channels while using a standard USB 2.0 protocol. Bruce Wahler politely agreed to spread his info to our lists, so all credits go to Bruce. ce ---------- ---------- Subject: OT -- USB History Date: Donnerstag, 16. Februar 2006 18:12 From: Bruce Wahler &lt;desp(a)mm.ed&gt; To: access-list(a)ampfea.org Hi All, [Warning: This post has little to do with the Virus TI per se. It might be of interest to some of you, though.] I was involved in the early USB efforts, working for a major PC manufacturer. The 3-tier speed approach of USB is a confusing -- and necessary -- part of the design. Early USB appealed to two groups: 1) manufacturers who wanted to simple, cheap way to untangle the rat's nest of wires that were growing behind computers; and 2) developers who wanted a better, more flexible connection than serial and parallel ports provided. In addition, the creators of USB had this grand vision of "USB everything": kitchen appliances, phones, televisions, you name it. USB attempts to satisfy all of these needs, but the goals of different markets are sometimes at odds with each other. Devices like mice can't afford to add even $1.00-2.00USD of product cost, because their customer base won't accept the price increase. On the other end, there's no such a thing as "too fast" for disk drives and networks. USB 1.0 (and 1.1) came out with Low- and Full-Speed specifications to try to bridge the needs of these two camps. Same connectors, same (or similar) cables, same hardware at the host (computer) end; all of the higher-speed functions had to be a layer on top of the basic ones. At the time of USB 1.0 (1995), the practical limit for cables and such was considered to be somewhere in the range of 10-15Mbit/sec. This wasn't a PHYSICAL limitation; it was governed by the cost of hardware (cables, connectors, ICs, etc.) compared to the amount of data being sent (<1GB). Unfortunately, USB 1.x took several years to gain acceptance. (PCs had the USB ports back in 1995, but there were no real peripherals nor OS support for 3-4 more years. One of my bosses used to refer to it as the "Useless Serial Bus.") By the USB really took hold (2000? 2004?), there were enough advances in technology and manufacturing to up the speed a great deal. Add to that the need to transfer more data, and the fear that FireWire would eclipse USB, and "Hi-Speed USB" was born. Hi-Speed USB follows the same rules as USB 1.0: faster protocols must work around the limits of slower ones, so nothing becomes truly obsolete. This is why a 12Mbit/sec Virus TI is still "USB 2 compliant." Some important things to know about Hi-Speed USB: 1. The GUARANTEED cable length is shorter (5m vs. 2m). With a quality cable, you might run further, but there's no whining if it doesn't work. This certainly limits the ability to use the Virus TI as both a recording platform and a performance synth at the same time. 2. Raw bandwidth numbers of Hi-Speed USB are deceptive. (This is also true of FireWire.) While the cable and ICs can support 480Mbit/sec., it takes great drivers, proper interrupt selection, and a relatively unused computer to use that bandwidth. Otherwise, it's a game of "hurry-up-and-wait." Sharing USB with slower devices also clouds the picture. 3. USB 2.0 enhancements focused on data storage. There weren't any high-speed audio extensions added. If Access had wanted to use 480Mbit USB audio, they would have had to develop and support it from scratch -- on both the Mac and PC. So, it's not just a case of adding a little product cost; it's a large development and testing challenge, too. Why weren't there audio extensions? Probably because the two "official" audio uses for USB -- Internet phones and digital USB audio -- didn't need them. The first one is fine with 12Mbit/sec, and the second one never really caught on. 4. The USB specifications were mostly written by big companies like Microsoft, IBM, Intel, and Compaq. They sunk a lot of resources into USB, and so their needs took top priority. None of those companies is known for professional audio gear -- they're computer companies, and USB audio was and still is a bit of an afterthought. (Quick: Name me one 'major' US PC manufacturer who sells a true MPC in their standard line? Anyone?) So, why not add the hardware (ICs) now, and write the OS support later? The approach rarely works, IMHO. Even in the computer industry, known for technology advances, hardware that is unused at product launch often remains forever unused. Why? Remember the old adage, "If it ain't broke, don't fix it" ? Well, updating software or firmware requires breaking that rule. And anyone who's written software will tell you that bugs crop up in the strangest places. While the updates are cool, there's often very little evidence that the efforts resulted in big sales increases. Thus, a small company like Access must be choosy when planning product updates. Regards, -BW -- Bruce Wahler Design Consultant Ashby Solutions™ http://consult.ashbysolutions.com 978.386.7389 voice/fax bruce(a)ashbysolutions.com _______________________________________________ access-list mailing list access-list(a)ampfea.org http://www.ampfea.org/mailman/listinfo/access-list <--- SUBSCRIBE/UNSUBSCRIBE DETAILS HERE Patches: http://www.ampfea.org/cool/stuff/access-list -------------------------------------------------------