Introduction to RAM

RAM is important. It is one of the reasons why computers work the way they do. For many of us, when deciding on buying on a new PC, the quantity of the RAM gives an idea if a machine is worth investing in.

But, what is RAM? Random-access-memory is used by devices to temporarily store data. It is quite different from hard drives and CDs; where the time it takes to read and write data is affected by physical location. With RAM, data is written and read approximately at the same speeds, regardless of physical location: Hence the name, random-access-memory. This synchronized performance gives RAM the advantage. But, RAM is volatile; therefore, if power is lost, its data is also lost.

Currently, random-access-memory is made up of transistors and capacitors, and it takes the form of an integrated circuit. But, earlier versions of RAM were sometimes mechanical [relays]; with the earliest using a cathode ray tube — which was featured in the Manchester Small-Scale Experimental Machine on June 21, 1948 (the unveiling of the first prototype of a stored- program computer). A DRAM chip, called, the intel 1103 (which is an IC RAM chip), was later introduced in 1970.

There are generally two types of RAM: static (SRAM) and dynamic (DRAM). And, both are volatile!

Static RAM is made up of transistor-memory cells, and it is mostly used as the CPU’s cache.  It is faster than DRAM and uses less power. But, static RAM is far more expensive to produce.

Dynamic RAM is made up of both transistors and capacitors. It is mostly used as the computer’s main memory. DRAM is not as fast as SRAM. It also requires more power when maintaining its storage. But DRAM is far cheaper; therefore, making it a better alternative when quantity is preferred over quality.

Upgrading is mostly done for DRAM chips; where they are easily removed and replaced. But, because of its integration within the CPU, SRAM is not usually upgradable.

There is a version of RAM, called ECC memory. This chip, which can be either SRAM or DRAM, has additional circuitry that detects and corrects memory errors; this feature does come with a production cost. Therefore, ECC RAM is not usually found in many consumer products; devices that require low tolerance for errors, for example, ATMs, RAM with ECC capability is a safer choice.

ROM is non-volatile: It does not require constant power when storing data. But, it does require special equipment when writing data. An alternative method combines both RAM and ROM into a single storage medium. Therefore, giving it the speed of RAM and the non-volatility of ROM. This hybrid storage is called flash memory and it can be found in devices such as USB drives, solid-state drives, and memory cards.

Having a gain in performance and at the same time requiring periodical power refreshments, places RAM in a unique situation.

Whether it’s the cache that is integrated into the CPU [SRAM] or the memory modules inserted into the motherboard [DRAM], RAM is always used for temporarily storing data (which will be eventually handed over to the CPU for processing). Because data can now be preloaded (from a slower storage) into the much faster memory, latency is greatly reduced.

Compared to earlier systems, today’s computers come with vast quantities of memory [RAM]. But even with so much temporary storage, the demand from programs can sometimes surpass the available memory within a system. When this occurs, a technique, called, Paging, is used instead. Paging takes a portion of the secondary storage (hard drive) and turns it into random-access-memory. This is sometimes referred to as virtual memory (and it helps to prevent the system from crashing if all of the RAM is used up). The main drawback to virtual memory is speed (it’s very slow). This is a result of the underlying storage medium–not RAM.   

So despite being volatile, random-access-memory can improve performance within a system. By acting as a temporary storage, data can now be per-loaded from the (slower) system’s main storage before it is handed over to the CPU.



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