Memory modules

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Memory Modules a broad term used to refer to a series of dynamic random access memory integrated circuits modules mounted on a printed circuit board and designed for use in personal computers, workstations and servers. A memory module is the computer part that holds the Random Access Memory (RAM), measured in megabytes or gigabytes. a megabyte being 1,000,000 bytes of storage, and a Gigabyte being 10,000,000,000 bytes of storage. All of these bytes are placed in small circuits on a memory module stick, making it easy for anyone to replace or add more RAM as the computer needs it.

Transcript of Memory modules

  • 1.a broad term used to refer to a series of dynamic random access memory integrated circuits modules mounted on a printed circuit board and designed for use in personal computers, workstations and servers. A memory module is the computer part that holds the Random Access Memory (RAM), measured in megabytes or gigabytes. a megabyte being 1,000,000 bytes of storage, and a Gigabyte being 10,000,000,000 bytes of storage. All of these bytes are placed in small circuits on a memory module stick, making it easy for anyone to replace or add more RAM as the computer needs it.

2. Types of Memory Module Dual in-line package memory SIPP memory, single in-line pin package memory SIMM, a single in-line memory module DIMM, dual in-line memory module SO-DIMM SDR SDRAM DDR, DDR2, DDR3 SDRAM TransFlash Memory Module 3. DIP dual in-line package (DIP or DIL) is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins. 2 parallel connecting pins socket circuit board 4. SIPP single in-line pin package was a type of random access memory. It consisted of a small printed circuit board upon which were mounted a number of memory chips. It had 30 pins along one edge which mated with matching holes in the motherboard of the computer. This type of memory was used in 80286 and some 80386 systems. It was later replaced by SIMMs, which proved to be easier to install. 5. SIMM single in-line memory module, is a type of memory module containing random access memory used in computers from the early 1980s to the late 1990s. It differs from a dual in-line memory module (DIMM), the most predominant form of memory module today, in that the contacts on a SIMM are redundant on both sides of the module. 6. SIMM 30- (top) and 72-pin (bottom) SIMMs. Early 30-pin modules commonly had either 256 KB or 1 MB of memory. 7. SIMM The first variant of SIMMs has 30 pins and provides 8 bits of data. They were used in AT (286), 386, 486, Macintosh Plus, Macintosh II, Quadra, Atari STE and Wang VS systems. The second variant of SIMMs has 72 pins and provides 32 bits of data. These appeared first in the early 1990s in the IBM PS/2, and later in systems based on the 486, Pentium, Pentium Pro, early Pentium II. 8. SIMM 30-pin SIMM Memory Module Pin # Name Signal Description Pin # Name Signal Description 1 VCC +5VDC 16 DQ4 Data 4 2 /CAS Column Address Strobe 17 A8 Address 8 3 DQ0 Data 0 18 A9 Address 9 4 A0 Address 0 19 A10 Address 10 5 A1 Address 1 20 DQ5 Data 5 6 DQ1 Data 1 21 /WE Write Enable 7 A2 Address 2 22 VSS Ground 8 A3 Address 3 23 DQ6 Data 6 9 VSS Ground 24 A11 Address 11 10 DQ2 Data 2 25 DQ7 Data 7 11 A4 Address 4 26 QP* Data parity out 12 A5 Address 5 27 /RAS Row Address Strobe 13 DQ3 Data 3 28 /CASP* Parity Column Address Strobe 14 A6 Address 6 29 DP* Data parity in 15 A7 Address 7 30 VCC +5VDC 9. DIMM dual in-line memory module, comprises a series of dynamic random-access memory integrated circuits. These modules are mounted on a printed circuit board and designed for use in personal computers, workstations and servers. DIMMs began to replace SIMMs (single in-line memory modules) as the predominant type of memory module as Intel P5- based Pentium processors began to gain market share. 10. DIMM While the contacts on SIMMs on both sides are redundant, DIMMs have separate electrical contacts on each side of the module. Another difference is that standard SIMMs have a 32-bit data path, while standard DIMMs have a 64-bit data path. Since Intel's Pentium many processors have a 64-bit bus width, requiring SIMMs installed in matched pairs in order to populate the data bus. The processor would then access the two SIMMs in parallel. DIMMs were introduced to eliminate this practice. 11. DIMM Two types of DIMMs: a 168-pin SDRAM module (top) and a 184-pin DDR SDRAM module (bottom). Note that the SDRAM module has two notches on the bottom edge, while the DDR1 SDRAM module has only one. 12. SO DIMM small outline dual in-line memory module, is a type of computer memory built using integrated circuits. SO-DIMMs (also written SODIMMs) are a smaller alternative to a DIMM, being roughly half the size of regular DIMMs. SO- DIMMs are often used in systems which have space restrictions such as notebooks, small footprint PCs (such as those with a Mini-ITX motherboard), high-end upgradable office printers, and networking hardware like routers. PC6400 DDR2 SO-DIMM (200 pins) PC3-10600 DDR3 SO-DIMM (204 pins) 13. Common Types of DIMM 72-pin SO-DIMM (not the same as a 72-pin SIMM), used for FPM DRAM and EDO DRAM 100-pin DIMM, used for printer SDRAM 144-pin SO-DIMM, used for SDR SDRAM 168-pin DIMM, used for SDR SDRAM (less frequently for FPM/EDO DRAM in workstations/servers, may be 3.3 or 5 V) 172-pin MicroDIMM, used for DDR SDRAM 184-pin DIMM, used for DDR SDRAM 200-pin SO-DIMM, used for DDR SDRAM and DDR2 SDRAM 204-pin SO-DIMM, used for DDR3 SDRAM 214-pin MicroDIMM, used for DDR2 SDRAM 240-pin DIMM, used for DDR2 SDRAM, DDR3 SDRAM and FB-DIMM DRAM 244-pin MiniDIMM, used for DDR2 SDRAM 14. 168-pin SDRAM On the bottom edge of 168-pin DIMMs there are 2 notches, and the location of each notch determines a particular feature of the module. The first notch is DRAM key position. It represents RFU (reserved future use), registered, and unbuffered (in that order from left to middle to right position). The second notch is voltage key position. It represents 5.0V, 3.3V, and Reserved 15. DDR SDRAM Double data rate synchronous dynamic random- access memory (DDR SDRAM) is a class of memory integrated circuits used in computers. DDR SDRAM (sometimes referred to as DDR1 SDRAM) has been superseded by DDR2 SDRAM and DDR3 SDRAM, neither of which is either forward or backward compatible with DDR SDRAM, meaning that DDR2 or DDR3 memory modules will not work in DDR- equipped motherboards, and vice versa. 16. CLOCK CYCLE & PREFETCH BUFFER Clock Cycle All computers have an internal clock in the form of a chip containing a crystal that vibrates at a consistent frequency when applied to electricity. This frequency is knows as the clock rate. Each vibration of the crystal represents one clock cycle. The clock cycle is the shortest amount of time in which the computer can execute an operation. The reliability of the clock rate allows for the synchronization of computer activities, including those of RAM and the computer's Central Processing Unit (CPU). Prefetch Buffer RAM is, essentially, a bunch of electrical switches or "transistors." Each transistor is attached to a capacitor, which is capable of storing charge. A closed transistor blocks current, leaving its capacitor empty, thus representing a "0." An open transistor allows current to flow through, charging its capacitor so it represents a "1." The transistors are situated into rows and columns. In older versions of RAM, the computer would have to send a different request each time it accessed data on a given row. A prefetch buffer reads not only the data requested, but also data adjacent to it on its row, thus providing the processor with more of the "datawords" it needs per memory access. 17. Comparison of Memory Module DIMM 18. DDR, DDR2 & DDR3 COMPARISON DDR DDR stands for Double Data Rate. Like SDRAM, it operates at the rate of the computer's clock cycle. However, unlike SDRAM, it can transfer data twice per clock cycle. It does this by using the rising and falling edges of the clock signal, also known as "double pumping" and employing a prefetch buffer capable of accessing two datawords at a time. This means that it can store and move a value in the same amount of time it takes SDRAM to do one or the other, effectively doubling the memory's speed. DDR2 DDR2 also utilizes the same double pumping technique as DDR. It achieves performance gains by using a prefetch buffer that retrieves four datawords per memory access. This allows it to transfer data four times per clock cycle (compared to twice in the case of DDR). Its improved efficiency allows it to consume less power than DDR. DDR3 Like all other forms of DDR, DDR3 transfers data twice per clock cycle. However, its prefetch buffer can access eight datawords at a time. Thus, it can transfer data eight times per clock cycle, giving it a maximum data transfer rate twice that of DDR2 while using less power. 19. TransFlash or SECURE DIGITAL is a non-volatile memory card format for use in portable devices, such as mobile phones, digital cameras, GPS navigation devices, and tablet computers. 20. The Secure Digital format includes three card families available in three different form factors. The three families are: 1. Original Standard-Capacity (SDSC) 1MB to 2 GB (some 4GB) 2. High-Capacity (SDHC) 4GB to 32 GB 3. eXtended-Capacity (SDXC) 32GB to 2TB The three form factors are the original size, the "mini" size, and the "micro" size TransFlash or SECURE DIGITAL 21. TransFlash or SECURE DIGITAL 22. Memory Hierarchy The levels of memory in computer, from fastest to slowest speed : 1. CPU 2. L1 Cache 3. L2 Cache 4. Main Memory 5. Virtual Memory 6. Disk 23. CPU The central processing unit is one of the most important components in the computer. It is where various tasks are performed and an output is generated. When the microprocessor completes the execution of a set of instructions, and is ready to carry out the next task, it retrieves the information it needs from RAM. Typically, the directions include the address where the information, which needs to be read, is located. The CPU transmits the address to the RAM's controller, which goes through the process of locating the address and reading the data. 24. Level 1 or L1 cache is special, very fast memory built into the central processing unit (CPU) to help facilitate computer performance. By loading frequently used bits of data into L1 cache, the computer can process requests faster. Most computers also have L2 and L3 cache, which are slower than L1 cache but faster than Random Access Memory (RAM). While this is a good strategy, the CPU can work faster than RAM, and to speed things along, you might think of L1, L2 and L3 cache as the go-betweens that anticipate what requests will be made of RAM, holding that data at the ready. When a request comes, the CPU checks L1 cache first, followed by L2 and L3 cache (if present). If the CPU finds the requested data in cache, its a cache hit, and if not, its a cache miss and RAM is searched next, followed by the hard drive. The goal is to maximize hits and minimize misses that slow performance. L1 CACHE 25. The main memory in a computer is called Random Access Memory. It is also known as RAM. This is the part of the computer that stores operating system software, software applications and other information for the central processing unit (CPU) to have fast and direct access when needed to perform tasks. It is called "random access" because the CPU can go directly to any section of main memory, and does not have go about the process in a sequential order. RAM is one of the faster types of memory, and has the capacity to allow data to be read and written. When the computer is shut down, all of the content held in RAM is purged. MAIN MEMORY 26. VIRTUAL MEMORY virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes the main storage available to a process or task, as a contiguous address space which is unique to each running process, or virtualizes the main storage available to all processes or tasks on the system as a contiguous global address space. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. 27. Permanent storage Permanent storage is hard drives, (both internal and external) and Cd's DVDs floppies + usb devices, including flash memory, because data that is stored on these devices remain there until physically changed, or deleted. The data is not lost when the power is turned off. 28. Memory Hierarchy