GeoRAM is a 512KByte memory expansion for the C64 and C128 from the company Berkeley Softworks. It is twice as high as a normal cartridge. In contrast to the REU this cartridge does not use DMA and blend pages of memory side in the first IO-area (start at $DE00). Which memory area is used, is controlled by a 5- and 6-bit register at the second IO-area (start at $DF00). One of the registers is at the even memory areas and the other one is at the odd memory areas.