System board is composed of the following components:
o Central processing unit: CPU (80386-20)
The CPU is a 32-bit microprocessor operated at 20 MHz clock
speed.
o Numeric data processor socket for the 80387-20 (optional).
o Real time clock: RTC (MC146818A)
The RTC continuously keeps the date and time powered by lithium
battery.
o Serial input output: SIO (NS16450)
The SIO controls the serial port.
o Keyboard controller: KBC (8042)
o Keyboard scan controller: SCC (8749)
o Cache memory controller: (82385-20)
o Memory
Read only memory: ROM 128 Kbytes (system BIOS)
Static random access memory: SRAM 32 Kbytes (cache memory)
o One super integration: SI (T4758A)
SI includes the two DMACs (equivalent to 82C37), two PICs
(equivalent to 82C59), and one PIT (equivalent to 82C54)
o Gate arrays:
The following gate arrays are used in the system board.
Memory controller gate array: GA-MCNT3
Memory bus latch gate array: GA-BLAT
Compatible bus latch gate array: GA-CLAT
Bus controller gate array: GA-BCNT2
<fig id=MMS\5200\52001_6.TIF>Page 1-6</fig>
1.2.2 Memory Board
Memory board is composed of the following components:
o Memory
Random access memory: RAM 2 Mbytes
Memory module socket: three 2-Mbyte memory module sockets
1.2.3 I/O Board and High Resolution Graphics Subsystem (HRGS) Board
I/O board and HRGS board are composed of the following components:
I/O board
o One supper integration: SI (T9761)
SI includes the floppy disk drive (FDD)/Parallel input and
output (PIO) controllers, one FDC (equivalent to TC8565), one
SIO (equivalent to NS16450), and I/O decoders.
o Variable frequency oscillator: VFO (MB4108A)
The VFO chip is used for FDD control logic.
o Basic graphics subsystem: BGS includes of the following ICs.
o Display controller gate array: PDC-GA
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