Questions: 1- Memory comes in a variety of speeds, latencies and timings. Ex. Sp
ID: 3674542 • Letter: Q
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Questions:
1- Memory comes in a variety of speeds, latencies and timings. Ex. Speed= DDR2 800 (PC2 6400), CAS Latency = 4, Timing = 4-5-4-15. What does the speed, CAS latency and timing stand for and why are they important?
2- What is the difference between ECC and non-ECC memory? In what type of PC or Hardware is ECC memory mainly used?
3- Both Windows and Linux use part of the hard drive as a swap file. Windows calls it a virtual memory setting. Why does the OS want a swap file or virtual memory and how does it work?
4- What is a RAM Drive and give an example of when one might be needed?
5- What is the PC BIOS for? Why do we transfer the BIOS to main memory upon starting a system?
6- Define the difference and give an example of volatile versus non-volatile memory.
7- We use Cache’s in many places on a PC. Define what a cache is, how it works and 2 places where caches may be found.
8- How do you determine what memory to purchase and how much to buy?
Explanation / Answer
1: a, Memory Timing: Determines/Measures the performance of the RAM using four parameters: CL,TRCD,TRP,TRASin units of clock cycle. Tras is often omitted and command rate is considered (1N or 1T).
b, Memory CAS Latency: Latency is the time delay that affects the speed of the RAM.The absolute system performance can be determined by Latency measured in nanoseconds.
c, Memory Speed : Rate at which the stable speed of the RAM works.It is mkeasured in cycle time or frequency.Speed determines the system accessibility. cycle time and frequency can be reciporced.
2. Non-ECC Memory: Non-ecc memory is commonly used for gaming and home pc’s. they are faster and cheap memories. they have lower latencies. Reliable and easy to use. Non-parity memory modules.Higher memory performed. detect but donot correct errors appropriately.
ECC Memory: Data accuracy is maintained. Parity memory module. more reliable. Detects and reports memory errors. Corrects errors without intervention of other operations. ECC requires stability and security. bit slower and expensive. Can only detect and correct single bit errors. For the use of ECC feature one have to use an ecc supported motherboard. these have higher latencies.
ECC is mostly used in: Servers,high-end systems, Scientific and financial Applications.
4. Ram Drive : A Ram drive(Ram disk) is a block of RAM that a computer’s software is treats it as a disk drive. It is also known as virtual RAM drive or software ram drive. A hardware RAM drive uses a separate hardware containing RAM, which is a type of a battery –backed solid-state drive.
A RAM disk is used in place of a standard disk bdrive because it is much faster. Data held in RAM is not retained after reboot. this is helpful where one want fast access but don’t necessarily want to store the data.
RAM disk guarantees the filesystem is always in RAM(once loaded). It also reduces the amount of RAM available to the rest of the system.
3. Swap File : A swap file is a space on a hard disk that is used as the virtual memory extension of a computers memory RAM. A swap file allows the computer operating system to pretend to have more RAM available.
The least recently used file in a RAM are swapped out so that new files can be stored(swapped in) to the hard disk. The units that are moved are called “pages” and swapping is called “paging”.
Advantage : It can be organized as a single contiguous space so tha less i/o operations are required to read or write a file.
Windows and LinuX operating systems use swap file so that the system administrator or user can usually change.
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