I have a S3C2440 single board EM2440-III.
My problem is that when I insert sd card 4G or 8G into the board, it not detect sd card. I insert sd card 2G and work OK. please help me to solve the problem.
Yeah, it does smell like a compatibility issue. In consumer devices we use SD/SDHC cards interchangeably while they are not really.
Looking at e.g. Sandisk's documentation, their upper limit for SD card is 2GB as well. Instead of NewEgg that you linked, checking Transcend's SD card lineup on their original site, the largest SD Standard is 2GB. I would have doubts whether the NewEgg one is genuine, there are way too many fake SD cards out there...
If the manufacturer says that it should support up to 32GB, maybe the best is then to get a couple of different capacity cards from different vendors, and get testing... They are quite cheap these days. Though it feels fishy to me that the manufacturer's website says one thing and the support says another. From experience, usually the support is wrong in most such cases.
I hadn't thought about fakery... very interesting point you are making: do not believe all you read on the Internet?
Yeah, totally not! It goes as anything else: "Trust but verify".I recommend Bunny Huang's (awesome hardware hacker and maker) post on MicroSD problems.
Also Googling "Fake SD Card" shows you the extent of the problem.