3 ms·

Holy Orders of Magnitude, Batman! "except this switch takes only one picosecond to change tracks." picosecond = one millionth of one millionth of a second (0.

by sanj 18y ago

Holy Orders of Magnitude, Batman! "except this switch takes only one picosecond to change tracks." picosecond = one millionth of one millionth of a second (0.000 000 000 001 seconds) "This means that in one second the switch is turning on and off about one million times." Huh? I thought it only took a picosecond!

hugh 18y ago
Ordinarily I'd blame journalistic innumeracy, but that's supposed to be a direct quote from the project head himself (a very smart guy, I used to work in the same building as him), so I assume it was a blunder by whoever prepared and sent out the press release.
Retric 18y ago
Time to switch is only part of the question you also need to send the data. If I where building a switch I would delay decoding the packet and just send the even packet's to one location and the odd packets to another and so you can double the time each location has to deal with a packet before it's got to decode the next one. Edit: and keep subdividing the packets like this until you can use fairly cheep processors to handle the load.
- sanj 18y ago
  Except that the next sentence talks about terabit capacity, which does require picosecond switching.
  - Retric 18y ago
    I don't think we are talking about the same thing, 1 picosecond * the speed of light = 0.2998 millimeters so a lightly longer cable and your packet is time shifted a few picoseconds. Anyway, The Switch 8800 has an impressive 1.44 Terabit-per-second backplane This does not mean it can route 1.44 trillion packets per second even if it can handle that many bits.
- hugh 18y ago
  As I understand it, it's not really switching at all. Different signals are sent simultaneously down the same fibre at slightly different wavelengths. This device splits the signal into its individual components. This is the same as what's already done, except currently the splitting is done electronically -- here, it's all done in optics, which makes it a lot faster.

by sanj 18y ago

hugh 18y ago

Ordinarily I'd blame journalistic innumeracy, but that's supposed to be a direct quote from the project head himself (a very smart guy, I used to work in the same building as him), so I assume it was a blunder by whoever prepared and sent out the press release.

Retric 18y ago

Time to switch is only part of the question you also need to send the data. If I where building a switch I would delay decoding the packet and just send the even packet's to one location and the odd packets to another and so you can double the time each location has to deal with a packet before it's got to decode the next one. Edit: and keep subdividing the packets like this until you can use fairly cheep processors to handle the load.

sanj 18y ago
Except that the next sentence talks about terabit capacity, which does require picosecond switching.
- Retric 18y ago
  I don't think we are talking about the same thing, 1 picosecond * the speed of light = 0.2998 millimeters so a lightly longer cable and your packet is time shifted a few picoseconds. Anyway, The Switch 8800 has an impressive 1.44 Terabit-per-second backplane This does not mean it can route 1.44 trillion packets per second even if it can handle that many bits.
hugh 18y ago
As I understand it, it's not really switching at all. Different signals are sent simultaneously down the same fibre at slightly different wavelengths. This device splits the signal into its individual components. This is the same as what's already done, except currently the splitting is done electronically -- here, it's all done in optics, which makes it a lot faster.