I bought a stick of 333MHz (256MB) and ended up with the lower density K4H280838C-TCB3 (still rated @333) chips...this stick wouldn't overclock much at all...and would barely do 333 at cl2 (2-2-2-5-1 on asus p4s333@166mem bus)...
I bought it because of this review:
German ddr333 comparison
but only asked if the chips were samsung, not knowing there were 2 different chips...
Anyway, the place I got it from was nice enough to have a stick of 512 w/ the K4H560838C-TCB3 chips as seen in the review...and sure enough, memtest is currently running for me at 187.5 (150fsb 4:5 cpu:mem ratio @ 2.9V)...running at 2.7V gave errors, but I still have a thermaltake cooling kit to put on this stick...
Just a heads up for those seeking 200MHz FSB and beyond...