Computer Architecture II - Advanced Concepts

Study Notes

Enables simultaneous execution of multiple programs or processes, enhancing overall system performance.
Virtual memory is a crucial component, mapping virtual addresses of programs to physical addresses in memory.

Functions as an illusion of a larger and faster memory, improving data access times.
Works on similar principles to virtual memory, such as locality in time and space, but operates at a different access time.

Virtual memory allows programs to execute even if they require more memory than physically available.
Protects data and programs from unauthorized access through effective address mapping.

Each program has its individual virtual address mapped to the physical memory space.
Addresses must be translated dynamically to ensure correct memory allocation and access.
Enhances memory management by acting similarly to a cache but requires different implementation due to access time discrepancies.

SRAM (L1): Access time of 0.5 ns, ideal for cache.
DRAM (L4): Access time of 10 ns, used for main memory, costs €4-6 per GB in 2015 and €4-14 in 2020.
Solid State Drive: Access time between 1-5 ms, prices dropped from €0.40 per GB in 2015 to €0.09 in 2020.
Hard Drive: Access time of 5-9 ms, significantly cheaper at €0.08 per GB in 2015 decreasing to €0.018 in 2020.

Frames: Logical segments that organize memory.
Addresses: Virtual addresses refer to program-specific locations; physical addresses correspond to real memory locations.
Address Translation: The dynamic process that maps virtual addresses to physical addresses, essential for system operations.

Similarities include cache blocks equating to pages and cache misses related to page faults.
A key difference lies in access times between DRAM and cache memory systems.

Enables simultaneous execution of multiple programs or processes to enhance performance.
Relies on efficient memory management techniques to optimize utilization of available resources.

Acts as a mechanism to create the illusion of a larger and faster memory space for improved access speed.
Functions similarly to virtual memory but operates at higher speeds and smaller scales.

Virtual Memory Tasks:
- Maps individual virtual addresses of programs to physical memory addresses, facilitating safe execution.
- Protects against unauthorized access, ensuring data security from other running processes.
- Provides support for programs exceeding available main memory by leveraging temporal and spatial locality.
Access Times and Cost of Memory Technologies:
- SRAM (L1) has the fastest access time at 0.5 ns.
- DRAM (L4) offers slower access at 10 ns, with costs fluctuating from €4-6 per GB in 2015 to €4-14 in 2020.
- Solid State Drives (SSDs) range from 1-5 ms in access time, with reduced costs from €0.40 to €0.09 per GB.
- Hard Drives (HDDs) have access times of 5-9 ms and even cheaper costs, decreasing from €0.08 to €0.018 per GB.

Basic Memory Terms:
- Memory is logically divided into frames.
- Virtual Addresses refer to program addresses; Physical Addresses refer to actual memory locations.
- Address translation involves dynamic mapping of virtual to physical addresses.
Cache vs. Virtual Memory:
- A cache block is referred to as a "Page" in virtual memory terminology.
- A cache miss is equivalent to a "Page fault," indicating that the requested data is not in the cache.
Access Time Differences:
- Access times differ significantly between DRAM and caches, impacting overall system performance during memory operations.