Memory Upgrade

I have an HP Pavilion a1110Y that I want to upgrade the memory in. The motherboard is an ASUS PTGD-LA, which is a dual-channel architecture board, supporting PC3200U memory. I currently have 2 512MB DIMMS, 1 DIMM in each of the 2 slot-pairs. I want to add at least 1GB more memory. I have had some issues with dual-channel architecture before. If I get 2 1GB DIMMS (the same kind), can I put them both in 1 slot-pair and the 512MB DIMMS in the other slot-pair? Or should I put 1 of each type of DIMM in each of the slot-pairs?

Here is a picture of your ASUS PTCD-LA motherboard.
from: http://h10025.www1.hp.com/ewfrf/wc/documen…l&site=null
📎ASUS_ASUS_PTGD_LA_MoBo_Pic.jpg

Notice the arrangement of RAM module sockets, – Blue - Black - Blue - Black

It is important to fit RAM of a matching set of two…. Both into the Blue, or Both into the Black module sockets.

Thus if you purchase 2 1GB DIMMS, Place them into the Blue module sockets.
Then place your existing pair of 2 512mb DIMMS into the Black module sockts

Thanks for this information. It helps. I have another question, however. Is there a difference between PC3200 and PC3200u?? If so, what is it?? The DIMMs currently in the HP computer say PC3200u. I purchased a pair of Patriot Signature Line 1GB, PC3200, 400MGz DIMMs, but the notch in the DIMM seems to be just a bit off and I could not seat them in the slots. Do I have to actually get PC3200u DIMMs??

You did purchase the wrong type of memory, but not only because of the "u" designation.

Your machine's motherboard does indeed support "dual-channel architecture" 4 x 240-pin DIMM sockets 533/400 MHZ DDR2 memory modules

That would be PC2 3200 non-ECC.

Here's an example of what fits your machine.
http://www.newegg.com/Product/Product.aspx…N82E16820134181