73 lines
2.3 KiB
Markdown
73 lines
2.3 KiB
Markdown
# Virtual Memory
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- Additional memory without adding physical RAM
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- simulates memory using storage devices
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- Useful when RAM is inusufficient
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- Hardware and Software implementations
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- Utilizes disk drive to store memory
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- ## Why Use Virtual Memory
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- Modern operating systems require a lot of memory
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- Not enough physical RAM to multiple apps
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- ## How Virtual Memory Works
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- Memory Management Unit (MMU)
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- Unneeded data in RAM moved to hard disk
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- Swap file or page file
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- Slower that RAM, although SSDs are better than hard disks
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- ## Managing Virtual Memory in Windows
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- Performance options -> Virtual Memory
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- ## Pros and Cons of Virtual Memory
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- | Pros | Cons|
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| Can improve system performance | Slower than physical RAM |
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| Increases capacity for multitasking | Consumes disk space |
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| Useful for large, memory-intensive applications | Can result in frequent hard disk access |
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| | Leads to poor performance if incorrectly used |
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- # Small Outline Dual In-line Memory Module (SODIMM)
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- Refers to its smaller footprint
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- Performs similarly to larger DIMMs
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- ## SODIMM Versions
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- DDR
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- DDR2
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- DDR3
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- DDR4
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- DDR5
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- ## DDR5
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- Released in 2020
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- Maximum DIMM size of 128GB
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- Lower voltage at 1.1V
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- 51.2 GB/s
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- # Double Data Rate 3 (DDR3) Memory
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- Twice the speed of DDR2
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- 240-pin DIMM or 204 SODIMM
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- Incompatible with previous generations
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- ## DDR3
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- Bus clock speed between 400 and 1066 MHz
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- Cycles four times per bus cycle
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- Transfers data twice per clock cycle
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- Bandwidth between 6400 and 17066 MB/s
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- MT/s (Million transfers per second)
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- e.g., DDR3-1600 - 1600 million transfers per second
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- # Double Data Rate 4 (DDR4) Memory
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- DIMM and SODIMM form factors
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- Twice the speed of DDR3
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- ## DDR4
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- 288-pin DIMM or 256-pin SODIMM
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- Incompatible with previous generations
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- Bus clock speed between 1066 and 2133 MHz
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- Bandwidth between 12800 and 25600 MB/s
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- MT/s from 1600 to 3200
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- # Double Data Rate 5 (DDR5) Memory
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- Lower Power consumption
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- Twice the speed of DDR4
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- ## DDR5
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- Lower voltage at 1.1V
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- Voltage regulators
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- Additional cost
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- 51.2 GB/s
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- MT/s from 3200 to 6400
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- ## DDR5 Enhancements
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- Four times the capacity of DDR4
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- Single DIMM maximum of 128 GB
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- Die stacking
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