Monday, August 21, 2000		On Hardware

A remember-all microchip named RAM

RAM or the random access memory is one of the most critical components of a computer. It is so termed because any storage location on it can be accessed directly by the processor.

RAM is placed in a computer in the form of a chip, which is fitted on the motherboard and keeps the data from the operating system and application programmes temporarily in the memory for easy access by the processor as and when it is required.

Physically, RAM is a small microchip on which the processor loads the temporary data. This data is directly interchanged by the processor with the RAM, through bus (data lines), which is present on the motherboard. Since both processor and the RAM are fixed on the motherboard, the data interchange is direct. Although, storage devices, like the hard disk and CD-ROM, also store the data and are connected with the motherboard through external cables, yet the access through the RAM is the fastest.

Unlike these devices, where the stored data stays forever, unless the user erases it, the data in the RAM stays temporarily and is erased when the computer is either rebooted or turned off. On restarting, the old data in the RAM gets lost and new data is loaded on it.

It is for this reason that computers need to be booted for better performance. Since the objective of the RAM is temporary storage therefore these have a small capacity in comparison to the hard disk.

At present, the computers are available with the memory of 64 MB. However, the capacity of hard disk is in gigabytes. The performance of a computer improves with higher RAM, since RAM is a short-term memory device, the access to which is much faster than that of the long-term memory device—the hard disk.

In the case of lesser RAM, as the short-term space gets filled up and the computer has to access the hard drive. frequently, which slows down the performance.

If the RAM of a computer gets filled up, then how does a computer work? In order to understand, take the example of a human brain. Any recent event is etched in the brain’s short-term memory. As the time passes, the event is overtaken with more recent happenings. This is transferred to the long-term memory. If you wish to recall something, you have to get it from the long-term memory.

Similar is the case with the RAM. The recent data used by the computer is loaded on it and if the RAM is full, the processor needs to continuously go to the hard disk to swap old data in RAM with new one. This way, the RAM never runs out of memory and the computer goes on working. For optimum performance, higher RAM is the key word as higher RAM reduces the number of times the processor reads the data from the hard disk, which takes much longer than reading data from the RAM. Technically, the access time taken by the processor is in nanosecond, whereas in case of the hard disk, access time is in millisecond.

Often, there is a lot of confusion between RAM and ROM. Where RAM is the random access memory, ROM is referred to as read only memory. Basically, ROM is "built-in" computer memory, which contains data that is being read only and not written. So, this read-only information is the necessary programme file, which is required to boot the computer and load the relevant file, each time the computer is switched on. Unlike the RAM, the data in the ROM is not lost as a long-life button battery, which is placed on the motherboard, guards it.

This was all about the academic aspect of the RAM. Regarding the practical aspect of the RAM, one should know that the physical size of the RAM is same for all computers and it does not differ with its capacity. So, a 64 MB RAM would be equal to a 32 MB or a 16 MB RAM, physically.

Now a days, SD-RAM is used in computers, which supports a maximum speed of 100 MHz, since the currently available bus speed in the majority of motherboards and processors is only 100 MHz. SD-RAM or Synchronous Dynamic Random Access Memory is actually the generic name for the various kinds of dynamic random access memory, which are synchronized with the optimum clock speed of the microprocessor. The speed of the SD-RAM is measured in MHz, which is also comparable with the bus speed.

Since, the RAM is based on the bus speed of the motherboard and the processor, the RAM undergone a lot of change over a period of time. Earlier, when the Pentium I systems were in force, the EDO-RAM was used. This RAM supported a maximum speed of 83 MHz, which was in tune with the motherboards and processors of Pentium-I generation. Most of those computers did not support the SD-RAM. Currently, the EDO-RAM cannot be used, though in cases where the chip speed is faster than 55 ns (nano seconds), it can be used with computers with 100 MHz bus speed.

The SD-RAM is primarily of two types, SIMM and DIMM.

SIMM or the Single in-line memory module contains one or more RAM chips on a small circuit board with pins, which connects it to the motherboard. SIMM normally has a 32 data bit path to the computer that requires a 72-pin connector. For the SD-RAM chips, which have a 64 data bit connection to the computer, SIMMs is installed in in-line pairs.

DIMM or dual in-line memory module is a double single in-line memory module, which has a 168-pin connector, and supports 64-bit data transfer. Since it uses better interface, it is commonly used and is the standard norm for this generation of computers.

These days 133 MHz SD-RAM are also in use and are supported in computers with a bus speed of similar capacity. Some other types of RAM are: CD-RAM (cache DRAM), RD-RAM (Rambus DRAM), ES-DRAM (Enhanced DRAM), whereas in most of the computers JEDEC RAM or the normal SDRAM is used.

For higher-end computers, which have a bus speed of over 133 MHz, higher-end RAM is required which includes, DDR SDRAM or double data rate SDRAM, which supports the speed of 200 MHz, ESDRAM, which is essentially a SDRAM plus a small amount of SRAM cache allowing a speed up to 200 MHz. Other such high-end RAM is SLDRAM, Protocol-based DRAM and DRDRAM.

In a majority of computers available currently, normal SD-RAM is being used.

For buying commonly-used RAM, there are several brands available in the market like Hyundai, Samsung, Simtronics, IBM and TechRAM. Technically, all these are standardised but one must insist on lifetime warranty as these have a better performance generally.