PORTIBM PC Portable (uses same BIOS as XT) 0100-0107 - PS/2IBM PS/2, any model POS (Programmable Option Select) Note: the default value for PORTIBM PC Portable (uses same BIOS as XT) 0102h is stored in CMOS(Complementary Metal-Oxide-Semiconductor) A type of integrated circuit design known for its low power consumption. 31h 0100 R POS register 0 Low adapter ID byte 0101 R POS register 1 High adapter ID byte 0102 RW POS register 2 option select data byte 1 (see #P0492) 0103 RW POS register 3 option select data byte 2 (see #P0493) 0104 RW POS register 4 option select data byte 3 0105 RW POS register 5 option select data byte 4 bit 7 channel active (-CHCK) bit 6 channel status 0106 RW POS register 6 Low subaddress extension 0107 RW POS register 7 High subaddress extension Bitfields for PS/2IBM PS/2, any model POS register 2, option select data byte 1: Bit(s) Description (Table P0492) 7 0 = unidirectional LPTAbbreviation for Line PrinTer. port 1 = bidirectional LPTAbbreviation for Line PrinTer. port 6-5 PS/2IBM PS/2, any model Model 50 and higher 00b = default LPTAbbreviation for Line PrinTer. port at 3BCh 01b = "" 378h 10b = "" 278h 11b = reserved 4 enable parallel port 3 serial port address =0 COM2 (02F8h, IRQ3) =1 COM1 (03F8h, IRQ4) 2 enable serial port 1 enable diskette controller 0 (MCA) =0 override bits 1,2,4 and disable devices 0 card enable (CDEN) 0 =1 VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. sleep bit, disconnects output drivers from VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. (usage for VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. without monitor) ---ET4000--- 7-4 reserved??? 3 video RAM(Random Access Memory) See also DRAM, SRAM. wait enable 2 ET4000: ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware. The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. wait enable 1 ET4000: I/O wait enable Note: access to this port is only possible when PORTIBM PC Portable (uses same BIOS as XT) 0094h bit 7 is low. SeeAlso: #P0493 Bitfields for Chips&Technologies 64200 "Wingine" setup register: Bit(s) Description (Table P0493) 7 enable access to extended registers (see #P0762) Note: on some C&T graphics chips, this register can be made read-only via XR70 (see #P0762) SeeAlso: #P0492