It depends on which particular black MacBook you have but you may be able to install up to 6gb of RAM inside a black MacBook. You would do this by installing one 4GB memory chip into one memory slot while with the other memory upgrade slot you install a 2 gb memory module.
The black MacBooks either max out at 2 GB of RAM or 4GB of Memory depending on what model you have. The later Apple MacBooks will run up to 6GB of memory unofficially, meaning that it’s not supported or documented by apple and some of the earlier models will recognize 3GB of RAM.
Personally, I don’t think it’s worth the bother to upgrade your Black MacBooks past what is recommended by Apple as I think you’re just asking for trouble. Just because you can, doesn’t mean you should.
The intel core duo black MacBooks released in 2006 will max out at 2GB of PC5300 DDR2 RAM. You will need to buy 2x1GB PC5300 DDR sodimms to get the maximum RAM for this black MacBook model
The intel core 2 duo black MacBook models also max out with 2GB of RAM and the same memory configuration is required: 2x1GB PC5300 DDR sodimms are needed to get the maximum ram
The intel core 2 duo black MacBooks with the ‘santa rosa’ processor will take more ram than the 2GB of predecessors and will recognize 4GB of ram by installing 2x2GB PC53000 DDR so-dimms.
the 2008 intel core 2 duo black MacBook will also take 4GB by replacing the standard memory that came from the factory with 2x2GB 4GB memory upgrades for black MacBook
So yes, you could squeeze either 3GB or 6GB into your black MacBook depending on what particular black MacBook model you have but it’s not something I can recommend. Some trusted memory vendors (OWC comes to mind) say that the larger memory will work just fine with the dark colored apple notebooks but I can’t recommend it and sleep at night.
But for the later black MacBooks there’s no reason why you can’t install 4GB RAM for Black MacBook and rest assured your black MacBooks will run just fine with the ram maxed out at 4GB.