Winter 18 CIS 314 Final A Name Sid 1 5 Draw 2 Input XOR Cir

Winter 18 Cis 314 Final A Name Sid1 5 Draw A 2 Input Xor Cir

Draw a 2-input XOR circuit using only AND, OR, and NOT gates.

Describe the functionality of each Y86 pipeline stage during execution of the andl rA, rB instruction in terms of the icode, ifun, rA, rB, valA, valB, valC, valP, valE, valM, srcA, srcB, dstE, dstM, cnd signals (you may also use M, R, and PC).

Briefly describe why the stall penalty for a pipelined Y86 ret instruction is 3 cycles.

Consider the following C procedure: void swap(int xp, int yp) { int t0 = xp; int t1 = yp; xp = t1; yp = t0; } Write Y86 code that implements the above C procedure. Comment your code.

Consider the following C function: int f(int a, int dest, int prod) { dest = prod ? 1 : 0; for (int i = 0; i dest = a[i]; } else { dest += a[i]; } } } Rewrite the above C function to minimize unnecessary function calls, memory writes, and if statements.

Consider a 32-byte direct-mapped cache with 8-byte blocks for an 8-bit machine (256 bytes of memory):

• Write a C function unsigned char getOffset(unsigned char address) that returns the cache offset for the specified address using bitwise operators (assuming the cache parameters above).
• Write a C function unsigned char getSet(unsigned char address) that returns the cache set for the specified address using bitwise operators (assuming the cache parameters above).
• If the following addresses are accessed in sequence, which addresses will result in cache hits and which will result in misses (assuming the cache parameters above and that the cache is initially empty)? For each address, show the tag, set, offset, and whether it resulted in hit or miss: 0xxxxxx24

Paper For Above instruction

The assignment requires addressing multiple facets of digital logic design, pipeline architecture, instruction execution, optimization of code, and cache memory management. Each part explores fundamental computer architecture concepts with practical coding exercises and theoretical understanding.

Firstly, designing a 2-input XOR gate using only AND, OR, and NOT gates emphasizes understanding basic logic gate functions and how complex logic functions can be realized using primitive gates. An XOR gate is essential in digital systems, especially in arithmetic operations like addition, where its properties facilitate the distinction between even and odd sums. By expressing XOR solely with AND, OR, and NOT, students reinforce their comprehension of Boolean algebra and gate-level implementation, foundational for digital circuit design.

Secondly, analyzing the execution stage of the Y86 processor during an 'andl rA, rB' instruction necessitates an understanding of pipeline architecture. Each pipeline stage (Instruction Fetch, Decode, Execute, Memory, Write Back) processes signals such as icode, ifun, register specifiers (rA, rB), values (valA, valB, valC), and control signals (cnd). The instruction flow involves fetching, decoding, calculating, accessing memory if needed, and writing results back to registers. Precise modeling of these signals at each stage provides insight into instruction processing latency, hazards, and data dependencies, crucial for optimizing pipelined CPU performance.

Thirdly, understanding why the 'ret' instruction in a pipelined Y86 architecture incurs a three-cycle stall highlights control hazard management. During a return, the processor must predict or wait for the return address stored on the stack. Since stack operations and jump target calculations involve multiple memory accesses and potential mispredictions, the pipeline must stall to ensure correct control flow, leading to a penalty of three cycles. This reflects the importance of branch prediction and hazard mitigation techniques in pipeline design.

Fourthly, rewriting the C function 'swap' into Y86 assembly demonstrates low-level programming and the understanding of memory and register operations. The approach involves loading pointers' values, swapping contents via temporary registers, and storing back to memory. Commenting code clarifies each step's purpose, reinforcing comprehension of stack operations, memory access patterns, and instruction syntax in Y86 architecture, vital for system-level programming and hardware-software interfacing.

Fifthly, optimizing a C function that multiplies or adds array elements based on a flag involves reducing unnecessary function calls and memory writes. By replacing 'len(a)' with an inlined calculation or a known size, eliminating redundant checks, and restructuring the loop, efficiency improves. The goal is to streamline control flow, minimize branching, and reduce memory traffic, illustrating performance tuning techniques relevant in software optimization and embedded systems.

Sixthly, analyzing a sequence of Y86 instructions involving memory moves and register operations explores pipeline hazards—specifically data hazards. When running without forwarding, stalls are needed to resolve data dependencies, leading to pipeline bubbles. With data forwarding, dependencies are mitigated by directly passing data between pipeline stages, reducing stalls. Drawing pipeline diagrams for both scenarios visually demonstrates the impact of forwarding on pipeline efficiency and hazard resolution strategies in modern CPU design.

Seventhly, in examining cache behavior in a 256-byte, 8-byte block, direct-mapped cache, functions to determine cache offset and set are implemented via bitwise operations based on memory address bits. Calculating which addresses result in hits or misses involves understanding cache mapping, tags, and replacement policies. Accounting for initial cache state and address sequencing helps assess cache performance, demonstrating principles of spatial and temporal locality, cache coherence, and memory hierarchy optimization.

In conclusion, the set of tasks cohesively covers the essential aspects of computer architecture: logic design, pipeline functioning, control hazards, low-level programming, optimization, and memory hierarchy. Mastery of these topics enables the development of efficient hardware and software systems, which are fundamental in advancing computing technology.

References

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