Hi, over 20 years ago, there was a software called RAM doubler. It used hard disk space to increase the size of the RAM. Given that SSD is fast, can we use part of SSD as RAM especially on MBP 2010 with only 8GB RAM max?
If you are referring to the actual product RAM Doubler - it would first handle how it loaded memory. Things were quite different then and these were the three things it did (best I recall)
Load only what apps really needed to work in RAM
Used a modified allocation of RAM that was akin to compressing data
if more RAM was needed, it would temporarily write to disk (this was the LAST choice)
As for SSD vs RAM, others here covered it quite well. The only thing one might be able to do is simply make sure all swap/scratch files point to the SSD and possibly temp files etc. These are volatile write/read operations with fair frequencies for some applications. In truth, 8 gigs should be sufficient for all but the hungriest of applications (See Adobe software as a prime example).
I am a big advocate of getting more RAM than one thinks they might need but if you have 8 gigs of RAM, the next best upgrade would be to acquire an SSD.