Cost, Performance, and Size Tradeoffs for Different Levels in a Memory Hierarchy*

Until recently, electronically addressable devices such as ferrite core, plated wire, semiconductor memories, and electromechanically addressable devices such as magnetic tapes, disks, and drums were the few technologies from which a computer system designer could build a memory system. A number of different new technologies and devices have been developed that close the "access gap"¹⁴between the two dissimilar technologies mentioned above. These include charge-coupled devices (CCD\´s),²bubble memories,⁴electron beam addressed memories (EBAM),¹⁷and domain tip propagation (DOT).¹⁶Other technologies like CMOS¹and integrated injection logic (I²L),⁹compete directly with the existing technologies. Table 1 (see p. 46) shows the possibility of a six-level hierarchy and some cost and performance projections for these technologies.