MacBook Pro (Mid-2009, 13", 2.26) Memory Upgrade Question

Question

I currently own a MacBook Pro (2.26; 13") (Mid-2009) with 2GB of memory. I purchased a single 4GB memory card that I plan to add in one of the slots. If I understand correctly that would leave me with a total of 5GB of memory (4GB   1GB). Is this workable?
I have heard rumours that both slots must have the same amount of memory. Regardless - will this be detrimental or an improvement?

Answer 1

Running Lion I would say go for more RAM. 2 GBs is Lion's minimum. If you run more than a couple of applications concurrently then you will quickly find yourself low on memory which would slow down the machine a lot more than the lack of matched pair RAM modules. I would say 4 GBs is a good compromise for casual uses. But if you're trying to run all the Adobe CS5 apps or all of the Office apps concurrently, then you'll be happier with 6 GBs of RAM. But it's hard to know what to suggest since only you know your operating situation, so here's some info that may help you make the decision.
About OS X Memory Management and Usage
Reading system memory usage in Activity Monitor
Memory Management in Mac OS X
Performance Guidelines- Memory Management in Mac OS X
A detailed look at memory usage in OS X
Understanding top output in the Terminal
The amount of available RAM for applications is the sum of Free RAM and Inactive RAM. This will change as applications are opened and closed or change from active to inactive status. The Swap figure represents an estimate of the total amount of swap space required for VM if used, but does not necessarily indicate the actual size of the existing swap file. If you are really in need of more RAM that would be indicated by how frequently the system uses VM. If you open the Terminal and run the top command at the prompt you will find information reported on Pageins () and Pageouts (). Pageouts () is the important figure. If the value in the parentheses is 0 (zero) then OS X is not making instantaneous use of VM which means you have adequate physical RAM for the system with the applications you have loaded. If the figure in parentheses is running positive and your hard drive is constantly being used (thrashing) then you need more physical RAM.
Adding RAM only makes it possible to run more programs concurrently.  It doesn't speed up the computer nor make games run faster.  What it can do is prevent the system from having to use disk-based VM when it runs out of RAM because you are trying to run too many applications concurrently or using applications that are extremely RAM dependent.  It will improve the performance of applications that run mostly in RAM or when loading programs.