I dont like to make advertisement for free but as a Machinedrum owner I was curious, here is the text from Elektrons collapsed site:
The +Drive divides a machine in 128 Snapshots, which allows for thousands of patterns, sounds and songs to be stored internally and more or less instantly recalled. The +Drive also makes it possible for the Machinedrum SPS-1UW+ MKII to host over 6000 ROM samples. The Monomachine SFX-60+ MKII can be loaded with more than 8000 DigiPro user waveforms.
A Machinedrum Snapshot can contain up to 128 patterns, 64 kits, 32 songs and 8 globals. If the Machinedrum is a UW model, each Snapshot also contains a sample bank. A UW MKII sample bank consists of 48 ROM sample slots. A UW MKI sample bank consists of 32 ROM sample slots.
A Monomachine Snapshot can contain up to 128 patterns, 128 kits, 24 songs and 8 globals. In the case of the Monomachine MKII, a Snapshot also contains a Digibank consisting of 64 DigiPro user waveforms.
Either load a completely new Snapshot or a single Machinedrum sample bank/Monomachine Digibank. When loading a new Snapshot, all data will replaced by new content. Loading a new sample bank/Digibank means all other content of the current Snapshot stays intact. Load times for both options are just a few seconds.
The +Drive gives the enormous advantage of having thousands of patterns and kits available. Change Snapshots during a live performance for a completely new session. Load a fresh Machinedrum sample bank or Monomachine Digibank and experiment with new sounds in your currently active patterns and kits. A +Drive opens up a world of new possibilities.
All Machinedrum and Monomachine models are possible to upgrade with a +Drive. When you buy a +Drive, you will receive detailed instructions how to send in the unit for the upgrade. Shipping back to you after the upgrade has been carried out is included in the price.