PURPOSE: To improve the extendability of a portable computer by making an internal memory capable of being easily extended without redesigning hardware logic.
CONSTITUTION: A ROM-EMS memory 100 including plural ROMs such as a DOS-ROM and an application ROM is mapped in extended memory address space independent of system address space, and each memory of the ROM-EMS memory 100 is accessed through the ROM-EMS window of the system address space. Accordingly, for instance, in the case that the bit width of a ROM-EMS address is 25 bits, the arbitrary memory in the extended memory address space of 32 Mbytes independent of a system address can be referred to through the window. Accordingly, as far as it is within the range of the 32 Mbytes, the ROM and a RAM can be freely added without redesigning the hardware logic.
SATAKE SHIGERU
MORISAWA SHUNICHI
