MEM 80C00000h - COMPAQ DIAGNOSTICS REGISTER Size: WORD Note: Writing to F000h:FFE0h seems to involve unlocking the memory by writing FEFEh to this address first. The write-protection can be reestablished by writing FCFCh to this address??? This was seen done by MS HIMEM.SYS. SeeAlso: F000h:FFE0h Bitfields for Compaq Diagnostics Register: Bit(s) Description (Table M0132) 15-10 unknown purpose (should remain set???) 9 =1 memory is read-write??? =0 memory is read-only??? 8 =1 to disable ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. replacement??? =0 normal??? 7-2 unknown purpose (should remain set???) 1 =1 memory is read-write =0 memory is read-only 0 =1 to disable ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. replacement??? =0 normal Note: Writing to F000h:FFE0h seems to involve unlocking the memory by writing FEFEh to this address first. The write-protection can be reestablished by writing FCFCh to this address??? Microsoft HIMEM.SYS was seen to do this. SeeAlso: F000h:FFE0h