When the OS runs low on RAM and swaps something out to disk, the memory compressor intercepts this, compresses the contents using a fast algorithm, but keeps it in RAM. Memory compression introduces a layer in between these: it partitions off a block of system memory for compression.

OSes that support virtual memory have a two-way split, between real physical RAM and virtual memory in a file on disk. Memory compression works by introducing a second level of swapping to the OS. Doubling your system's RAM sounded like a great deal in 1994, when a 4MB SIMM would cost $170 – £230 today. This crazy-sounding idea first appeared with Connectix's RAMdoubler in 1994, an add-on for Mac OS 7.6 – a slightly easier proposition as classic Mac OS didn't have true preemptive multitasking. What SoftRAM 95 claimed to do was software memory compression – on-the-fly compressing data in RAM so that your OS has more fast storage available than without the software. There are few lessons about modern software in there as well. One of the most consistently interesting and entertaining Microsoft blogs, Raymond Chen's Old New Thing, recently covered the dissection of a best-selling bit of software for Windows 95 – SoftRAM 95.

Microsoft fixit for ie 11