I have perused the web, but am unable to figure out what parameters affect the "real" max amount of memory one can use in a particular laptop. It has been my experience that the manufacturer's claimed maximum can be exceeded, but I am not sure how to predict which memory types and combinations will work. For example, a Compaq C571NR will work with one Micron 2GB DDR2 800 128x8 SODIMM even though each slot is supposed to be limited to 1GB. It will also work if one adds a Transcend 512MB DDR2 533 SODIMM CL4, yielding a total of 2.5GB. However, it will not work with two of the 2GB Micro SODIMMS (blank screen), nor with one 2GB Micron SODIMM and one 1GB Nanya 128x64 DDR 666. I have successfully put in over-spec amounts of RAM in a Compaq C762NR and an Averatec 2300, so I know this can be done.
I am just using trial and error. On some machines it works to add RAM above the supposed max, and on some machines it doesn't. I assume that a combination of BIOS and chipset govern this. It would be helpful to know exactly what information is needed in order to determine home much memory (lets say up to 4GB) a particular laptop will really support, and in what configuration.
The significance of this question is that using over 2GB RAM will significantly reduce paging to the hard drive, and this reduced disk thrashing can dramatically speed up the system (presuming the paging file, MFT and boot files are defragged and placed together at the front of the hard drive, which can be done through modifying the scripts in MyDefrag and running them from a cold CD boot to BART PE or WIN PE).
So I would appreciate if anyone could give a step by step approach to determining the real maximimum memory of a particular laptop and the specific configuration(s) that will work.
The optimal speed of the memory to use is covered in a separate thread, and was a bit over my head technically, but I imagine that the brute force approach (without overclocking) is just to meet or exceed the memory speed specs for the laptop and to use identical kits if there is dual channel memory capabilities. In the C571NR this latter feature is not present.