Memory difference in Dual Channel,loses speed?

[feas2407]

Hi Gang, I have an old Dell Dimension 4700 3.8ghz p4, HT enabled, WD Caviar 300gb hd, 2gb DDR2 SDRAM, cd/dvd opticals, etc... It is compatible with either (pc2-3200 266mhz) or (pc2-4300 533mhz) mem. I had '2' 1gb (pc-6400 800)'s in it and it was fast, but way oversped and had boot errors. I found a set of 533's on ebay for less than $20, so i got them. The only thing i saw slightly off was the memory description, advertising the mem.'s as pc2-4200, as opposed to most makers labelling it as pc2-4300, wikipedia says its the same basically...! I am running Dual Channel atm, and wonder why my Piriform* Speccy* program shows 2gb memory but only at 266mhz instead of the 533? The new sticks have 8 chips per side(16 total), whereas the old pc2-6400 800's and the original Dell 256Mb stick have only chips on 1 side. I have only a basic understanding of this, but i think it has to do with capacity/distribution?? or how the cpu access the memory. Thank You for any insight on this.