The VIC-20's RAM is expandable through the cartridge port via a Super Expander Cartridge (or simply, RAM Expander). RAM cartridges were available in several sizes: (with or without an included BASIC extension ROM), , , and , the latter two only from third-party vendors. The internal memory map is dramatically reorganized with the addition of each size cartridge, leading to a situation where some programs only work if the right amount of memory is present (to cater to this, the cartridges had switches, and the cartridges had software setups, allowing the RAM to be enabled in user-selectable memory blocks). Since the VIC-20 was designed to use SRAM rather than DRAM, the system board has no provisions for DRAM refresh.