INTRODU C'l' ION This chapter provides a general description of the 486 system. Figure 4-1 shows a block diagram of the main subsystems which make up the 486. These include the CPU board and the hard disk controller board which are briefly described below. CPU BOARD The CPU board is a multi-functional subsystem that contains the main processor, the I/O processor, the floppy disk drive controller, 256 Kbytes of main memory, the memory management unit, the memory arbitration logic and the I/O ports for all peripheral interfacing. 8~186 MICROPROCESSOR The 486 Computer System is designed around the Intel 80186 microprocessor.
It performs most of the central processing unit functions, with the capabil ities for Direct Memory Access (DMA), programmable Timers, and Interrupts. It is an integrated circuit housed in a special 68 pin package. 4-1