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jaclaz

The (meta-sata-pata)physics of USB Transfer

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The sound (well below what the human ear can perceive) made by the spinning asterisks on some cable types can be very similar to the mating cry of werewolves...

The possibility of this make me think of sparkly vampires. I understand that they seem to go hand-in-hand with werewolves nowadays. While I am curious I REALLY don't want all of the trouble this may bring.

However the pale-skinned, dark haired beauties they attract might be nice :D

http://verydemotivational.files.wordpress.com/2010/05/129194375038528447.jpg

Edited by Kelsenellenelvian
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Guys, going over and over with that kind of jokes is not too helpfull IMO, however I was wondering if rloew was also joking saying that transmitting zeros was slower than transmitting ones so I looked up a bit and from what I understand (perhaps erroneously) by briefly reading about NRZI encoding used for USB data transmission it would be that the more there are bit changes the slower the transmission.

I wasn't joking!

But I wasn't talking about "transmitting" zeroes, I was talking about "writing" zeroes.

Nobody has gotten even close yet.

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In such a scenario, physics tells us how if you give a stronger push, the pushed object will acquire greater speed
Why stop here? USB pin 1 provides 5V max. If the USB specifications were modified to be driven at 12V (volt is a unit of pressure), we can utilize the VBUS to additionally accelerate the data rate by 2.4 times faster over the existing rate.
BUT what the good guys did was simply to use smaller characters
With bit compression, we can further reduced reduce the size to its most basic form. 0, 1.
And sent them vertically, here you can see how the fatter 0's may slow down transfer, since they go more tight in the pipe
Any advantage of transmitting them lengthwise is negated by their adjacency to each other which allows them to take advantage of aerodynamic drafting (a la stock car racing). Transmitting them as originally diagrammed always result in shorter data length, and therefore faster rate.

Tightness of the pipe can be resolved with a wider gauge cable. USB data conductor wires use a twisted pair (figure 1). The problem with this configuration is twofold. Transmitting data through a swirly twist as opposed to a straight line is inherently slower. The gauge is also narrow. Data can only flow in single file (figure 2). Rather than have each pin in its own wire, all pins can be propelled en mass over a multi/fat pipeline, and applying multi-quad shielding to compensate for not using twisted pair, which also helps stiffen the cable, thus avoiding sharp bends or kinks (figure 3).

USB Type A Connector
__________
| ______ |
| [______] | 1 5V --> ------------------------------------------------------------------------
| _____ | _ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _
| [_____] | 2 Data- --> \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/ \/
| [_____] | 3 Data+ --> _/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\__/\_
| ______ | Twisted Pair
| [______] | 4 GND --> ------------------------------------------------------------------------
|__________|

Figure 1: USB data lines in a twisted pair

==================================================================================================

USB Type A Connector
__________
| ______ |
| [______] | 1 5V ------------------------------------------------------------------------
| _____ |
| [_____] | 2 Data- 01 11 00 10 00 01 00 11 00 01 10 00 00 11 00 01 00 00
| [_____] | 3 Data+ --> 01 00 01 11 01 00 01 10 01 01 00 00 01 11 01 10 01 11
| ______ | Twisted Pair
| [______] | 4 GND ------------------------------------------------------------------------
|__________|
Transmission Order: ...............................................................987654321
(using dots to represent two digit numbers due to lack of space)
Figure 2: Data transmitted slowly over 72 individual bits through a twisted pair

==================================================================================================

USB Type A Connector Extra Shielding
=======================================
__________ =======================================
| ______ | ------------> 0 0 0 0 0 0 0 0 0
| [______] | 1 12V ------------> 1 1 1 0 1 1 1 1 1
| _____ | ------------> 0 0 0 1 0 0 0 0 0
| [_____] | 2 Data- ------------> 0 0 0 0 0 0 0 0 1
| [_____] | 3 Data+ ------------> 1 1 1 0 0 1 0 1 0
| ______ | ------------> 1 0 1 0 1 0 0 1 0
| [______] | 4 GND ------------> 0 0 1 0 0 1 0 1 1
|__________| ------------> 0 1 1 0 1 1 1 0 0
=======================================
=======================================
Extra Shielding
Transmission Order: 9 8 7 6 5 4 3 2 1

Figure 3: Data transmitted quickly in 9 bytes yielding the output of:
01010011 01001110 01000001 01001011 01000101 00100000 01001111 01001001 01001100

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Ah, you're talking about UPB (Universal Parallel Bus)? :ph34r:

GL

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