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Random Access Memory Interview Questions and Answers


This page contains the collection of Random Access Memory Interview Questions and Answers / Frequently Asked Questions (FAQs) under category Computer Hardware. These questions are collected from various resources like informative websites, forums, blogs, discussion boards including MSDN and Wikipedia. These listed questions can surely help in preparing for Random Access Memory interview or job.

What is SDRAM?
Synchronous dynamic random access memory (SDRAM) is dynamic random access memory (DRAM) that is synchronized with the system bus. Classic DRAM has an asynchronous interface, which means that it responds as quickly as possible to changes in control inputs. SDRAM has a synchronous interface, meaning that it waits for a clock signal before responding to control inputs and is therefore synchronized with the computer's system bus. The clock is used to drive an internal finite state machine that pipelines incoming commands. The data storage area is divided into several banks, allowing the chip to work on several memory access commands at a time, interleaved among the separate banks. This allows higher data access rates than an asynchronous DRAM.

What is RDRAM?
Direct Rambus DRAM or DRDRAM (sometimes just called Rambus DRAM or RDRAM) is a type of synchronous dynamic RAM. RDRAM was developed by Rambus inc., in the mid-1990s as a replacement for then-prevalent DIMM SDRAM memory architecture.

RDRAM was initially expected to become the standard in PC memory, especially after Intel agreed to license the Rambus technology for use with its future chipsets. Further, RDRAM was expected to become a standard for VRAM. However, RDRAM got embroiled in a standards war with an alternative technology - DDR SDRAM, quickly losing out on grounds of price, and, later on, performance. By the early 2000s, RDRAM was no longer supported by any mainstream computing architecture.

What is feRAM?
Ferroelectric RAM is a random-access memory similar in construction to DRAM but uses a ferroelectric layer instead of a dielectric layer to achieve non-volatility. FeRAM is one of a growing number of alternative non-volatile random-access memory technologies that offer the same functionality as flash memory. FeRAM advantages over flash include: lower power usage, faster write performance and a much greater maximum number of write-erase cycles. Disadvantages of FeRAM are much lower storage densities than flash devices, storage capacity limitations, and higher cost.

What is ECC memory?
Error-correcting code memory (ECC memory) is a type of computer data storage that can detect and correct the more common kinds of internal data corruption. ECC memory is used in most computers where data corruption cannot be tolerated under any circumstances, such as for scientific or financial computing.

ECC memory maintains a memory system effectively free from single-bit errors: the data that is read from each word is always the same as the data that had been written to it, even if a single bit actually stored, or more in some cases, has been flipped to the wrong state. Some non-ECC memory with parity support allows errors to be detected, but not corrected; otherwise errors that may occur are not detected.

What is tRCD timing?
tRCD is the number of clock cycles delay required between an active command row address strobe (RAS) and a CAS. It is the time required between the memory controller asserting a row address, and then asserting a column address during the subsequent read or write command. tRCD stands for row address to column address delay time.

What is tCAS?
tCAS is the number of clock cycles needed to access a certain column of data in SDRAM. CAS latency is the column address strobe time, sometimes referred to as tCL.

What is tRP?
tRP is the number of clock cycles needed to terminate access to an open row of memory, and open access to the next row. It stands for row precharge time.

What is tRAS?
tRAS is the minimum number of clock cycles needed to access a certain row of data in RAM between the data request and the precharge command. It's known as active to precharge delay. According to Mushkin.com, in practice for DDR SDRAM, this should be set to at least tRCD + tCAS + 2 to allow enough time for data to be streamed out. [1]. It stands for row address strobe time.

What is shadow ram?
Shadow RAM is a copy of Basic Input/Output Operating System (BIOS) routines from read-only memory (ROM) into a special area of random access memory (RAM) so that they can be accessed more quickly. Access in shadow RAM is typically in the 60-100 nanosecond range whereas ROM access is in the 125-250 ns range. In some operating systems such as DOS, certain BIOS routines are not only used during the boot or startup of the system, but also during normal operation, especially to drive the video display terminal. In Windows and OS/2, however, these routines are not used and the use of shadow RAM is not necessary. In some systems, the user can turn the use of shadow RAM off or on.

What is RAM parity?
RAM parity checking is the storing of a redundant parity bit representing the parity odd or even of a small amount of computer data typically one byte stored in random access memory, and the subsequent comparison of the stored and the computed parity to detect whether a data error has occurred.

The parity bit was originally stored in additional individual memory chips; with the introduction of plug-in DIMM, SIMM, etc. modules, they became available in non-parity and parity (with an extra bit per byte, storing 9 bits for every 8 bits of actual data) versions.

Random Access Memory(RAM) Interview Questions:
1. How does a RAM function?
2. What are differences between RAM and ROM?
3. What is a flash memory?
4. What are the different RAM standards/versions?
5. What is the purpose of RAM in a computer?
6. What kind of memory is a RAM categorized as?
7. How does the CPU and the RAM communicate?
8. What is the function of the control lines in RAM?
9. What are the different types package forms?
10. How is the total memory on a ram stick calculated?
11. What is bursting?
12. What is buffered RAM?
13. What is pipelining in reference to RAM?
14. What is SO-DIMM in reference to RAM?
15. Why are Wait states used?
16. What are banks in reference to RAM?
17. What are the functions of the RAM IC`s?
18. What is the difference between RAM and cache memory?
19. How is the maximum addressable memory calculated?
20. What does the 400 Mhz signify in a ram specification?
21. What are the various capacities in which a RAM is available?
22. How can a DDR1 ram be identified from a DDR2 ram module physically?
23. Explain the basic concepts and hierarchy of memory?
24. Why is RAM also known as volatile memory?
25. State the differences between DDR1, 2 and 3.
26. What is SDRAM?
27. What is RDRAM?
28. What is feRAM?
29. What is ECC in reference to ram?
30. How does ECC works?
31. What is tCL timing?
32. What is tRCD timing?
33. What is tRP timing?
34. What is tRAS timing?
35. In a Ram description DDR 2 1066mhz “2.5-3-3-8” what do the numbers in quotes signify?
36. Explain the command rate in reference to RAM?
37. What is the tRC timing?
38. What is the tRTW/tRWT timing?
39. Explain the tRDA?
40. What is the limit of RAM capacity in a 32bit OS?
41. What is shadow ram?
42. Explain what is the memory wall problem?
43. Explain the dual channel architecture?
44. Explain the triple channel architecture?
45. What is RAM parity?
46. What is the Unified memory architecture? Explain.
47. What is virtual memory?
48. What is a phase change memory?
49. Explain the refresh operation in a dynamic RAM?
50. Can two different RAM speed modules be used together?

Explain the virtual memory?
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage such as random-access memory and disk storage, allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which behaves like directly and contiguous addressable read/write memory.

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