Yeah,
i`m now sure that when the boards came out that i gb sticks didn`t exist so that they could only have a max of 2 x 512 /1gb .
asynchronous means that information is read seperatly, improving the read/write speed by 10-20%, the data is split between the two sticks, it doesn`t work tri-syncronously (that hasn`t been invented yet)
[if your in the bios, you could try differant CAS Ratings (2 being the fastest read speed setting), try slowing it down to 3...