| 摘要 |
A personal computer is disclosed which has the capability of transferring the contents of the computer's 16-bit read only memory (ROM) into the computer's 32-bit random access memory (RAM) by mapping the ROM contents in the same memory locations in RAM. The use of the dual mapped ROM obviates the poor performance which was previously obtained by the use of an 8-bit or 16-bit ROM with a 32-bit microprocessor. The use of the dual mapped ROM permits the 32-bit microprocessor to make calls to the basic input/output system (BIOS) at the rate of 32-bits instead of an 8-bit or 16-bit rate. A logic means is provided to test as much RAM as is necessary to store the BIOS. Thereafter the BIOS is transferred from ROM to RAM, the RAM test continues, the initial machine states and registers are set, and diagnostics are performed by the microprocessor making calls to the BIOS at a 32-bit rate to dynamic memory instead of a 16-bit memory. The logic means also locks out the RAM where the BIOS is stored to prevent any inadvertent changes or deletions to the RAM locations where the BIOS is stored. The dual mapped RAM system disclosed also permits the operator to unlock the writing functions to the RAM where the BIOS is stored and thus permits the operator to change the BIOS in the event a programming bug is found after the computer is delivered or in the event the operator wants to change the characteristics of the machine's BIOS. |
