Properly set my Rivatuner to show double memory clock 8800 gts 512 mb

Evga 8800 GTS 512 (G92Core) Vs MSI 8800 GT 512 (g92core)?
i have a EVGA 8800 gts 512
and
also a MSI 8800 gt 512


does any one know why does my 8800 gts clock at 970 mhz memory clock suppose to say 1940mhz only shows it at half.
my 8800 gt runs at 600 core clock and 1800 mhz for memory clock at stock.

both are g92 cores. 512 ddr3
ive used rivatuner to look at both memory core clock speeds i know if i divide 1940 by 2 i get 970. but i dont understand why does my 8800 gt report 1800mhz vs my 8800 gts reports only half 970 and y doesn't my 8800 gt report half also when i plug it in.

same goes with my Ntune.