I bought a sapphire 6570 SKU# 11191-00-20G which got an effective memory clock of 1800mhz. But instead i received the sapphire 6570 SKU# 11191-26-20G which seems to have an inferior m. clock and i'm still trying to find out its m. clock because if i open the box i can't return the product.
So i contacted sapphire tech support with a ticket: ( messages start from bottom )
Sorry, but this information is incorrect. DDR3 multiplies the base memory clock by 2. It is "double data rate" or "double pumped".
It can't have a 1800 effective clock with a base clock inferior to 900.
1800mhz effective and you need to take that and divided by 3 which gives you around 600mhz so with DDr3 you need to times it by 3 to get you some where close or over to 1800mhz.
As far as I can tell it should have 900mhz DDR3 / 1800mhz effective. There's a GDDR5 model as well with 1000mhz / 4000 effective (GDDR5 is quad rate).
So, definitely weird that he'd say it's 667mhz. 667 x 3 doesn't equal 1800mhz either. I'd suggest phoning to get some real results. I had issues with online/email support for a Logitech keyboard, but calling them I was able to clear the issue up pretty quickly.