The use of a translation look-aside buffer further slows down the access since it adds another level altogether.Increase in access time due to an extra memory reference is added.It is known as the theoretical speedup of the pipeline. The formula to calculate speed up is as follows:Īs n approaches infinity, S approaches k. The speedup gained using the pipeline is the ratio of the time taken without pipeline to the time taken using the 5-segment pipeline. Without a pipeline the time required to process a task in 1 cycle is.įor, n tasks the number of cycles required = Therefore, to complete n tasks using a k-stage pipeline requires:.The remaining tasks emerge from the pipeline one per cycle, which implies a total time for these tasks of.
Also assume we have n instructions or tasks to process. Time taken by a 5-segment pipeline using clock cycles to process a task = 40 ns. Time taken by a non-pipelined system to process a task = 200 ns. When Intel moved to the IA32 ISA, backwards compatibility was a requirement for its large customer base.
The small set of registers used in the 8086 did not allow for much data to be stored in these registers hence the to-operand instructions (as opposed to three as in MIPS). This is the main reason Intel uses variable-length instructions. Intel created it IS for the 8086 when memory was very expensive, which meant designing an instruction set that would allow for extremely compact code. The MIPS ISA is different from the Intel ISA partially because the design philosophies between the two are so different. However, only the base addressing mode can be used explicitly. Addressing Modes: A variety of modes like immediate, register, direct, indirect register, base, and indexed are allowed.Three instruction formats are available: immediate, register and jump. ISA: Allows five types of instructions: simple arithmetic, data movement, control, multicycle and miscellaneous.In the R10000, the number of pipeline stages depends on the functional unit through which the instructio.erscalar. The R4000 and R4400 have 8-stage superpipelines. Pipelining: R2000 and R3000 have 5-stage pipelines.Addressing Architecture is Word-addressable, three-address mode.In all, 17 addressing modes were provided. Addressing Modes: Intel processors allowed for the basic addressing modes as well as certain combinations of those.Pentium II had 12-stage pipeline, Pentium III had a 14-stage pipeline and Pentium IV had a 24-stage pipeline. Stages were Prefetch, Instruction Decode, Address Generation, Execute, and Write Back. Pipelining: The Pentium I had two 5-stage pipelines.Addressing Architecture is two-addressing mode.Byte Storage is Little Endian notation.and any other instructions that do not fit into the other categories.
Procedure calls are special branch instructions that automatically save the return address.Ħ) Special purpose Instructions: These include string processing, high-level language support, protection, flag control, word/byte conversions, cache management etc. Skip instructions are essentially branches with implied addresses. These include branches, skips, procedure calls, returns and program termination. The basic schemes for handling I/O are programmed I/O, interrupt-driven I/O, and DMA devices.ĥ) Instructions for Transfer of Control: Controls instructions are used to alter the normal sequence of program execution. The output instruction transfers data from a register or memory to a specific port or device. The input instruction transfers data from a device or port to either memory or a register. Examples are ADD, s, setting specific bits, and toggling specific bits.Ĥ) Input/Output Instructions: These vary greatly among architectures. This class of instructions also affects the flag registers. As with data movement instructions, there are sometimes different instructions for providing various combinations of register and memory accesses in different modes. Many instruction sets provide different arithmetic instructions for various data sizes. Examples of this type are MOVE, LOAD, STORE, PUSH, POP etc.ģ) Arithmetic Operations: They include those instructions that use integers and floating point numbers. Data is moved from memory into registers, from registers to registers, and from registers to memory, and many machines provide different instructions depending on source and destination. 1) data movement, arithmetic, Boolean, bit manipulation, I/O, transfer of control, and special purpose.Ģ) Data movement: These are the most frequently used instructions.