By "Live USB" i mean a USB flash drive or anything of that sort. i wonder about the differences in CD versus USB. Are there cases where the USB version is faster?

if you want fast, use puppy or DSL, loads into memory.

Ditto for Slax. If you can get a live distro (depending on its size and your RAM) to load entirely to memory, it will be very quick.

Access time and transfer speed are both faster via USB2 versus optical mediums by default, this applies to anything stored on these mediums be it data or an operating system which is basically just data also. An optical drive can be faster than USB1.

The optical drive is mechanicle, anything with moving parts will always be slower than flash memory which is similar to RAM memory, but the USB flash drive is slower than RAM because it is further away from the processor and the bus is normally slower than the bus between RAM and the processor.

There are many types of computer memory, the speed of each type is normally synonymous with the size/amount of each.

1: The L1 cache, the smallest amount built into the processor, fastest.
2: The L2 cache, used to be installed in slots right next to the processor similar to RAM, nowadays it is built into the processor like the L1 cache, normally in larger amounts than the L1 cache, not as expensive as L1 technology, second fastest.
3: RAM memory, installed in slots next to processor on the mother board, kinda expensive, third fastest.
4: USB flash memory, much further away from the processor, fourth fastest.
5: Virtual memory, on the hard drive, controllers involved, much longer seek and access time due to mechanicle parts, speed differs depending on where on the drive the data is stored.
6: Hard drive, user data storage area, similar speed as virtual memory, depends on which area of the drive data is stored.
7: Optical drive, slower than hard drive because of spin up on demand compared to always spinning hard drive, allot more error correction needed.
8: Floppy and tapes, turtles at the back of the pack.

Of all the live distro's I've tried, these two seem the fastest. Puppy seems to be a little more complete than DSL, and has excellent hardware support. Though I've found DSL quite good in the respect too.

you can install puppy to a USB stick very easily.

Go check out my post here and see how fast my stuff boots off USB.

( http://www.linuxquestions.org/questi...-works-714322/ )

lots to choose from-make sure you check out the screenshot on reply#92.
Remember after reading that the last 2 download links-
billix-0.24-redux.zip
dsl-embedded-redux.zip
have not been successfully burned to CD-R, they both boot, but it can't find the dsl image-though the 1st CD did...? In billix-0.24-redux.zip if you make a cd it will still boot everything but DSL.

ALL USB VERSIONS OF ALL DOWNLOADS WORK.

Also, use the failsafe option at boot and DSL will boot faster.
( "dsl failsafe" )
I think the more HW detection they do, maybe that lengthens the boot sequence...?