Solid State Disks - Level 5 cache

Last month I had the pleasure to spend 2 hours in the car with Klaus Grieger. Klaus and myself know each other from ObjectDesign and Versant. Right now he is a partner with CIMT AG in Germany. As always talking to him was invigorating. He is one of the most innovative people I know.

The topic of the drive was the future of Solid State Disks (SSDs). His thought was/is that with the arrival of in-expensive, fast SSDs we can potentially rethink the way we structure memory and storage in general. Right now, we "load" executables from a "disk" into "main memory". What if, we turn the disk into a level 5 CPU cache, means programs never get loaded and/or started. They get installed into "memory" and will stay there all the time. Instructions get fetched into lower-level CPU caches on as needed basis. This would/could probably work for instructions, but not for data. Means for data you would still needs a disk with a file-system.

Hhhhmmmmmm, ... can somebody help me to think this through?