iRamDisk uses a portion of memory (ram) to create a volume displayed as an ordinary disk. The access time for data stored in memory are then incomparably reduced (several tens of times depending on configuration) and the hard drive (or SSD) is no longer solicited.

In practice:
The downside is that your computer has less RAM (4 to 16GB in general) of disk storage capacity (512GB to 1TB) added to this volatility RamDisk. In general, the RamDisk is used in cases where you want a very fast access to files and / or in the case of optimizing your hard drive for temporary files (cache of browser, Xcode, etc ... ) but also to reduce the impact of these files on a disk ssd whose life is limited.

Limitations: 7-day trial.

Requirements:
OS X 10.6.6+
64-bit Intel