My ageing hand-me-down MacBook (late 2007 - 1GB RAM) has been serving me well - it ended it's OS X life in the Autumn of last year and has been running Linux Mint 17 ever since - we call it the MintBook. Linux has been a saviour. Making the shift was easy enough (having used GNU/Linux before - mainly in Raspberry Pis and web servers), the ease of software development has been greatly improved (bar Xcode of course!) and it has basically resurrected an almost dead laptop.
However, 1GB of RAM really isn't good enough to run as a multi-purpose development/recreational machine. I could put Ubuntu on a Pi 2 model B and have practically the same results. My family is in the Apple ecosystem and as such we have quite a few 'older' Macs - primarily laptops. Recently one of the MacBook Pros died completely, not responding to safe mode and I couldn't even get into the BIOS. It was time for it to go. I disassembled it and removed the RAM cards (2x 2GB), then on a hunch I decided to see if they were the same kind as the MintBook's. I could have just gone online and looked up the serial numbers, but where’s the fun in that? Lo and behold, on dis-assembly of my machine, they were exactly the same type - except 4x the RAM! The next step (whilst fingers were being crossed) was to swap them over & reboot!
Needless to say the MacBook Pro still failed to run but boot time on the MintBook has decreased from 30s to about 5s and the same with most applications! I was going to run some benchmark tests by swapping the RAM back to their original position, running some tests, swapping them back again and re-running the tests. Strangely when I inserted the old RAM cards back into the MintBook and fired it up to run the tests, the MacBook Pro had done something strange - the cards now don't work in the MintBook any more! Weird! Thankfully the MacBook Pro's RAM still worked in MintBook so all was well, I just had to ditch the speed test comparison idea.
Soon after I had swapped the RAM cards, I decided to take a look inside one of our slightly newer MacBook Pros - the one that Dad spilled coffee on and which now crashes intermittently, usually when someone or something switches on hardware acceleration. On removal of the RAM however, I discovered they were completely different from the other ones and were no use in MintBook. 8GB RAM would have been good (if MintBook could have taken the extra of course)! Never mind, as I now have a substantially faster laptop which is much quieter and doesn't get nearly as warm! I am now considering switching from Mint to Ubuntu as the UI is much nicer... but then again UbuntuBook really doesn't sound as good.