On Sat, 12 Mar 2005, Laurent Daudelin wrote: > on 12/03/05 19:16, Zoltan Batiz at [EMAIL PROTECTED] wrote: > > On Mar 12, 2005, at 4:03 PM, Laurent Daudelin wrote: > >> >> on 12/03/05 18:19, Zoltan Batiz at [EMAIL PROTECTED] wrote: [snip pondering usb limit of 127 being arbitrary]
> >> It's not an arbitrary number. It has to do with computer programming > >> maths. > >> For the same reason that memory comes in multiple of 64. 128, 256, 512, > >> etc., and not 25, 50, 75. The root is the binary system that is the > >> basic > >> unit by which a computer can compute... > >> > >> -Laurent. > >> -- > > Oh ok, so what you are saying is that nobody actually tried connecting > > 127 devices to their system. Someone just came up with the number due > > to a mathematical formula? > > No, I'm not saying that. What might have happened is, in the protocol, they > identified some kind of ways to represent the unique address of a device on > the bus. In other words, the USB protocol is made of a set of commands, > which are basically a series of 0s and 1s. In the protocol, they probably > reserved 7 bits to represent the address, like 0000000. So, with 7 digits, > if you try all combinations of 0s and 1s you can have, you will come to the > total of 127 different combinations. I'm not an electrical or hardware > engineer, I'm a software engineer, and I think that's why they came up with > 127. Now, if you ask me why they choose 7 bits, then I wouldn't know. Maybe > some restrictions on the electrical side, or in the chip that sends and > receives those bits and convert them, I really don't know... > > Now, does that make more sense or did I make everything worst? Nope, but it's 8 bit, I believe: 2^0 = 0; 2^1 = 2; etc Zeros are people, too! ;-) -- Non Illegitimi Carborundum -- G-Books is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Check our web site for refurbished PowerBooks | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> G-Books list info: <http://lowendmac.com/lists/g-books.html> --> AOL users, remove "mailto:"; Send list messages to: <mailto:G-Books@mail.maclaunch.com> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/g-books%40mail.maclaunch.com/> --------------------------------------------------------------- iPod Accessories for Less at 1-800-iPOD.COM Fast Delivery, Low Price, Good Deal www.1800ipod.com ---------------------------------------------------------------
