I'm not familiar with that particular Mobo, but some of them need registered ram to see more than a 256 meg chip. Has to do with addressing, I forget why. This isn't the link I was looking for, but it talks some about the differences.

http://support.crucial.com/scripts/crucial.exe/solution?11=010131-0006&130=000980973033&14=&2715=&15=0&2716=0&57=search&58=&2900=aZV2s13dK2&25=6&3=reg istered

pay particular attention to the part about the "horizontal small chips" in this next quote - it may help you find out if your 512 is registered or not.

"Most PCs will accept only unbuffered SDRAM. Registered SDRAM is primarily used in servers and was designed for memory modules with 32 or more chips. If you are unsure whether your motherboard or PC supports registered SDRAM, simply look up your system in our Memory Selector. It will tell you which types of memory your system accepts.

You can tell if you have registered SDRAM by looking at one of the modules currently installed in your system. If it has one or more small chips mounted horizontally, you have registered memory. If not, you have unbuffered memory.

Keep in mind, unbuffered and registered modules are not interchangeable. When you install registered SDRAM, all of the modules installed in your PC should be registered."

Also, when I feed Crucial's memory config module a TUSL2-C, the largest module returned is a 256 - maybe that's all the board can handle per slot... Steve

Hi steve thanks for the reply the motherboard according to the specs supports up to 512 mb of pc100/pc133 sd ram non ecc,the stick i got from crucial is a 512 stick unbuffered non parity pc 133 sd ram,thats the one that shows up as 256,when i put the two sticks of pc 100 sdram unbuffered non parity they show up as 512,so the diference between the two is one is a 512mb single stick pc133,and the other is two 256mb sticks of pc 100.hope that may shed some light

that is werid that the crucial site says the max that board can handle is 256 tha manual says 512

phalic...check your Bios to make sure you have it set to 133 bus speed instead of 100....
It's all described in the manual for the Asus board..that's one thing I like about Asus..their manuals rock!
Opus

If your Mobo says it supports UP TO 512, and it has three slots, then it probably only supports 256 chips in EACH SLOT - in fact, I doubt if you could get the third slot to work at all if you had a pair of 256's in the first two slots. If the fact that the two 256's work isn't proof enough for you, try going to Asus.com and downloading the manual if you don't already have one. Read the part involving inserting ram chips very carefully to see if they mention what size INDIVIDUAL chips the board supports. Usually, I do this for people since I know where to go in a site, etc - but I absolutely HATE Asus's site for downloading manuals, they don't support "save target as", so you have to keep hitting the page down key to keep the manual from stopping. (I have a very slow connection) So, check your manual or download one. I'm pretty sure you'll find that it does NOT support 512 all in one chip... Steve

Steve you hit the nail on the head i just got two 256 sticks and the mb sees it now.The board was brand new so i do have the manual it states "sdram 8,16,32,64,128,256,512x1 for each socket,go figure ,but the one difference between the 512 stick and the 2x256 sticks is the 512 was cl=3 ram wich according to crucial is a slower ram ,but i havent found anything in the mb manual yet that states the board doesnt take cl=3 ram.but antway im in the process of applying opus's tweaks for 2000(great job opus!),so i should be up and runnin soon,thanks again guys for all the help and info ,you rule!!!