The 1999 PowerBook G3 Series computer has its Mac OS ROM image stored in RAM. This removes approximately 3 megabytes of RAM from availability for other uses. In effect, a system with 64 megabytes of RAM appears to have only 61 megabytes available. Some portion of the missing 3 megabytes is offset by having fewer patches in RAM. Other mechanisms are being explored in an attempt to minimize the impact of ROM-in-RAM.