When immediate is greater then 1, assembler generates several RCL xx, 1 instructions because 8086 has machine code only for this instruction (the same principle works for all other shift/rotate instructions). Algorithm: shift all bits left, the bit that goes off is set to CF and previous value of CF is inserted to the right-most position. The Intel 8086 (GNU FDL 1.2) 1978: Intel introduces the 16-bit 8086 microprocessor. It will become an industry standard. 1979: Intel introduces a lower-cost version of the 8086, the 8088, with an. The 8085 was an 8 bit data/16 bit address processor. (The same as the 8080, but with a few important differences, like a built-in serial port.) The 8088 was 8 bits data/16 bits address, the 8086 was 16 bits data/16 bits address. And the opcodes were different than the 8080/8085.
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I needed to write a piece of code which checks the microprocessor platform it works on. The code is to tell if it is simulatd on an 8088 processor or 8086 one.
I've got an idea but I'm confused with the implementation . The key to this problem is using the instruction queue as the length varies in 8088 from 8086.
16-bit chips differ from their 8-bit bus versions in their Bus Interface Unit design. The instruction queue on 16-bit chips is 6 bytes long, while on 8-bit versions it is 4-bytes long. To test the length of instruction queue, we shall write a routine that modifies the instruction 5 bytes away from the current one (the one that actually modifies another one). The modified instruction can be NOP and it can be changed to INC register. If the instruction was executed as NOP, we have 6-byte queue (16-bit chip). If it was executed as INC, we have 4-bye queue (8-bit chip).Can anyone help me to implement this ?
another question ...after the jmp instruction the queue becomes embty.When exactly would the bytes of code accumulate in the instruction queue???
In the changing world of technologies, the devices used are also changing. Let us take a look at the changes between 8085 series of microprocessors and 8086 series of microprocessors.
| Serial No. | 8085 microprocessor | 8086 microprocessor |
|---|---|---|
| 1 | The data bus is of 8 bits. | The data bus is of 16 bits. |
| 2 | The address bus is of 16 bits. | The address bus is of 20 bits. |
| 3 | The memory capacity is 64 KB.Also 8085 Can Perform Operation Upto 2^8 ie. 256 numbers. A number greater than this is to taken multiple times in 8 bit data bus. | The memory capacity is 1 MB.Also 8086 Can Perform Operation upto 2^16 ie. 65,536 numbers. |
| 4 | The input/output port addresses are of 8 bits. | The input/output port addresses are of 8 bits. |
| 5 | The operating frequency is 3.2 MHz. | The operating frequency is 5 MHz, 8MHZ,10MHZ. |
| 5 | 8085 MP has Single Mode Of Operation. | 8086 MP has Two Modes Of Operation. 1. Minimum Mode = SingLe CPU PROCESSOR 2. Maximum Mode = Multiple CPU PROCESSOR. |
| 6 | It not have multiplication and division instructions. | It have multiplication and division instructions. |
| 7 | It does not support pipe-lining. | It supports pipe-lining as it has two independent units Execution Unit (EU) and Bus Interface Unit (BIU). |
| 8 | It does not support instruction queue. | It supports instruction queue. |
| 9 | Memory space is not segmented. | Memory space is segmented. |
| 10 | It consists of 5 flags(Sign Flag, Zero Flag, Auxiliary Carry Flag, Parity Flag, Carry Flag). | It consists of 9 flags(Overflow Flag, Direction Flag, Interrupt Flag, Trap Flag, Sign Flag, Zero Flag, Auxiliary Carry Flag, Parity Flag, Carry Flag). |
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8088 Processor