I've been working lately with some old AGP graphics cards, to see how well do I fare in a completely CPU bottleneck free platform, and where the processor clocks aren't as important as in other platforms.
Well, to my surprise, when submitting scores some of the cards I work with don't discrimine between 64 or 128bit bus widths.
On newer PCI Express cards this doesn't pose that much of a threat, but on AGP that memory bus width can (and does) affect performance quite a lot.
For instance, take this FX5200 submission I made:
I ran the card to the clocks that gave me the best performance (305/500 - 250 DDR).
Now look at, for instance, this submission here:
He gets more than 2000 points more, while running at remarkably lower clocks.
The only difference between our cards is the bus. He has a 128bit-wide bus while I run a 64-bit narrow bus.
What I mean is, there is no contest for 64bit card users if there are 128 bit versions, because with little effort, a 128 bit card can easily score a 30% more points than a 64bit one overclocked to hell and beyond.
Thanks for your understanding!