Some of you may notice that on eBay sellers selling Dell Inspiron 6400 showing it has 4GB of RAM and the Dell Inspiron 6400 official systemboard showing it can go up to 2GB of RAM memory.
Official Dell website confirms that 6400/E1505 can go up to 2GB with a 2GB memory slot single module.
I done some research in eBay sellers and technical expert and it confirms that 50% of Inspiron 6400/E1505 system motherboard can go up to 4GB of memory (2x2GB DDR2).
I have tested myself to find out it was true by buying Samsung 4GB DDR2 SODIMM memory (2x2 GB memory) from eBay. The seller was a genuine seller (I won't name the eBay ID person) which I did and testing it when I already have the maximum of 2GB.
The results was successful and confirms that some can go up to 4GB of memory instead of 2GB and my laptop can go up to 4GB. I wouldn't recommended anyone to try it because Dell says 2GB memory capacity is due to safety limitations and if you try it on your Dell Inspiron 6400/E1505 laptop. Get a Samsung model because people recommended to me.
And one more thing: DO IT AT YOUR OWN RISK DON'T COME TO ME IF SOMETHING GOES WRONG WITH YOUR LAPTOP.
If you do get it to work you may notice of Windows XP or Vista saying 3.25GB out of 4 which because OS limitations and 768MB is for the system board to run optimized.
This might only works on Intel Chipset and updated BIOS to make this works.
ebay Link
