the 80486SX is almost identical to an 80386 with a cache of 8K bytes. No. Figure 3.5.b shows the structure of the inner core microprocessor 80486. If this is compared to the architecture of 80386 no differences were observed. The most notable difference between the 80386 and 80486 is that almost half of the 80486 instructions are executed in one clock period instead of the two periods that the 80386 requires to run.


Like the 80386, the 80486 contains 8 registers of 32 bits for general purposes EAX, EBX, ECX, EDX, EBP, EDI, ESI and ESP. These records can be used as records for the information of 8 16 or 32 bits or to address a location in the system of memory .

The records of 16 bits are the same set found in the 80286 and are assigned AX, BX, CX, DX, BP, DI, SI and SP. The 8-bit registers are AH, AL, BH, BL, CH, CB, DH and DL. In addition to the general purpose registers the 80486 also contains the same records that the 80386 segments which are: CS, DS, ES, SS, FS and GS. Each is 16 bits wide as in all previous versions of the family .


The IP accesses a program located within the memory 1Mbyte in combination with CS or EIP to direct a program in any location within the memory system 4Gbytes.In the operation in protected mode segment registers work to keep selectors as they did in the microprocessor 80286 and 80386.