128 bit vs 256 bit

[Neck]

I've decided to buy a Sapphire Atlantis Radeon 9800PRO 128MB DDR for my new rig, but I found two versions of it, one as 128 bit and one that says 256 bit.

So, a few questions:
1. What is that 128 bit or 256 bit measuring?
2. What is the difference?
3. Is 256 bit worth the price difference?

 

[scottchen]

That is the memory bandwidth and YES it's WORTH IT!!

<A HREF="http://forums.extremeoverclocking.com/myrig.php?do=view&id=17301" target="_new">My PC</A>

 

[Neck]

Wow, thanks for the speedy reply!!