Assignment 10

Due: 10:45am, Thu Apr 17th, 2025

Note: Make reasonable assumptions where necessary and clearly state them. Feel free to discuss problems with classmates, but the only written material that you may consult while writing your solutions are the textbook and lecture slides/videos. Solutions should be uploaded on Gradescope. Show your solution steps so you receive partial credit for incorrect answers and we know you have understood the material. Don't just show us the final answer. We require that answers be typed up and not hand-written.

Every homework has an automatic penalty-free 1.5 day extension to accommodate any health/family-related disruptions. In other words, try to finish your homework by Thursday 10:45am to keep up with the lecture content, but if necessary, you may take until Friday 11:59pm.

1. In a cache side channel attack (as in Spectre), how does the victim leave a secret-dependent footprint in the cache? How does the attacker extract this secret? (20 points)
2. Answer the following questions about virtual/physical memory.
   • Does the program code produce virtual or physical addresses? (5 points)
   • Why is the program's virtual memory address converted into a physical memory address? (5 points)
   • How does the hardware do an efficient translation from virtual to physical address? (10 points)
3. Consider a 3-processor multiprocessor connected with a shared bus that has the following properties: (i) centralized shared memory accessible with the bus, (ii) snooping-based MSI cache coherence protocol, (iii) write-invalidate policy. Also assume that the caches have a writeback policy. Initially, the caches all have invalid data. The processors issue the following five requests, one after the other. Create a table similar to that in slide 11 of lecture 24 to indicate what happens for every request. (40 points)
   • P2: Read X
   • P2: Write X
   • P1: Read X
   • P3: Write X
   • P1: Read X
4. Read some of the following blog articles about interesting problems in computer architecture. Write a 100-200 word paragraph describing what you learnt from one of these articles. (20 points)
   1. Persistent Memory - A New Hope
   2. Computer Architecture Research in Space
   3. Battle for Secure Caches
   4. Think Globally, Design Deliberately
   5. The Future of Datacenter Cooling