Okay I give up, my memory is - wait for it - 5ns and designed to run at 200Mhz (400 on powerstrip/coolbits), exactly HALF the speed of a 128Mb Ultra (I finally learnt how to read the speed off the chips like you guys probably did all along
This Samsung page is great ;
Here's the sad tail, dunno why it doesn't list 400Mhz for 2ns though ;
Part Number Max Freq. Max Data Rate Interface Package
K4D551638D-TC2A 350MHz 700Mbps/pin SSTL_2 66pin TSOP-II
K4D551638D-TC33 300MHz 600Mbps/pin SSTL_2 66pin TSOP-II
K4D551638D-TC36 275MHz 550Mbps/pin SSTL_2 66pin TSOP-II
K4D551638D-TC40 250MHz 500Mbps/pin SSTL_2 66pin TSOP-II
K4D551638D-TC45 222MHz 444Mbps/pin SSTL_2 66pin TSOP-II
K4D551638D-TC50 200MHz 400Mbps/pin SSTL_2 66pin TSOP-II
K4D551638D-TC60* 166MHz 333Mbps/pin SSTL_2 66pin TSOP-II
I wrote down K4D551638F, not ending in D, but I think it was a typo since samsung don't have that part.
Anyway there you go, 256Mb FX 5600 Ultra cards DO exist, they DO have the version 2 flipchip ultra gpu, and their memory is HALF the speed of a 128Mb one.
Anyone want a cheap card?