Memory clock on 5900u??

[Radicus]

Im so confused by the gforce fx cards. I was looking at the 5900u's and 5700u's on newegg. the core/mem clocks on the 5700u is 475/900. on the 5900u the core/mem clocks are 450/850. I'm sure theres a logical reason for this, im just to ignorant to know what it is:p could someone shed some light on this subject for me?

[weta]

Radicus: The GeForce FX 5900 Ultra has eight pipelines, where as the 5700 Ultra only has four.
Memory bus width is another deciding factor, 256bit/32byte for the 5900U and 128bit/16byte for the 5700U.

[Radicus]

OOH ok. thx