1-to-4 Mbyte SIMM adaptor

Memory upgrades for PCs can present unexpected problems. For instance, if you are upgrading with 4-Mbyte SIMMs (single-in-line memory module), the existing 1-Mbyte SIMM will be useless in most cases. A waste of money? Not if you build the circuit shown here, which enables four 1-Mbyte SIMM-modules with eight or nine DRAM chips, to act as a slngle 4-MByte SIMM, and occupy only one memory expansion socket. The circuit is not suitable for use with three-chip SIMMs.