DRAM memory is the abbreviation for Dynamic RAM. As you would suspect, this means that DRAM is a kind of RAM. It is used in computer processors and other hardware. While other types of RAM exist, DRAM memory is the most commonly used. In fact, DRAM is so common in consumer-grade PCs that it is simply called “the RAM” in most situations.
What is DRAM?
In this type of RAM, each bit of data is stored in an unique capacitor within a small integrated circuit. The capacitor can be either full of charge or discharged. These two states are used to stand for the two values of the bit, typically called zero and 1. Since even so-called “nonconducting” transistors and capacitors will always drip a tiny amount, the capacitors slowly discharge. The information eventually is lost unless the charge in the capacitor is periodically refreshed.
This need to refresh the charge is what makes DRAM memory “dynamic” as opposed to other types of “static” memory, called SRAM. SRAM is more expensive to manufacture than DRAM, but it is also faster, so it is only used in situations where speed is more important than cost, such as for the cache memory of a processor.
If the power source is removed, DRAM loses its information relatively quickly. This is what is called “volatile memory”. This is why you lose your unsaved work when your computer shuts down. There are other types of memory that won’t lose their data when the power goes away, such as the Flash memory seen in portable data drives, but these are a lot slower than DRAM and wouldn’t work for general use in a computer. They also tend to be bulkier when measured in physical size per bit.
How Does DRAM Work?
DRAM is extremely simple in structure. It consists of only one capacitor and one transitor per bit of memory. This is opposed to four to six of each in the more-expensive SRAM. The simplicity of DRAM means that it can be packed extremely densely onto a circuit board.
Due to the nature of the DRAM circuits, the exact number of circuits (which translates to bytes of data) per unit of DRAM is always a whole number exponential power of two. For example, a 512 MB memory module contains 2 to the power of 29 bytes (512 multiplied by 2 to the 20th power), or exactly 536,870,912 bytes of storage. That’s a lot of capacitors!
Since there are lots of DRAM circuits on a circuit board, and they need to be constantly recharged to keep from losing their information, DRAM uses a lot of power. Different hardware systems have a variety of ways of managing this power drain.
History of DRAM Memory
The first DRAM was invented in 1968. It was invented by a man named Robert Dennard. However, there were examples of DRAM in other products before his patent was filed. For example, there is a calculator model from the Japanese company Toshiba from 1966 that made use of this type of memory.
While Robert Dennard was the first one to official put a DRAM circuit together, the invention of this type of memory was inevitable given the trajectory of computer hardware development. Integrated circuits were appearing in computer hardware starting in the early 1960s because they were much smaller and less expensive than other conventional memory types.
The first DRAM circuits based on Dennard’s patents were sold by Intel in 1968. However, it was Honeywell Computers that moved DRAM technology forward next. They began selling a 3-transistor cell which allowed for more bytes per board.
Intel, Honeywell, and then MOSTEK began competing for market share for DRAM components. Eventually, Japanese manufacturers entered the DRAM market. They were able to produce better products for a lower cost and as a result took over the DRAM market in both Asia and the United States.
Applications and Usage of Dynamic RAM
As you can see, dynamic random access memory has been available for many years. It has been used since the days of the earliest home computer models. There is an interesting piece of trivia about DRAM versus processor speed over the same time period, though.
Since the invention of DRAM, the speed of this type of memory has doubled. This sounds good until you compare it to the speed of internal processors over the same time period. Processing speeds have increased by a factor of 40!
The reason for this difference has to do with how DRAM works. Because DRAM depends on each capacitor-transistor circuit holding onto its charge until the data can be refreshed, development of DRAM has focused on minimizing power leakage from the circuits rather than on increasing speed.
The speed of static RAM (SRAM) is a bit higher than that of dynamic RAM (DRAM) and compares better to that of the speed of processors. However, SRAM is much more expensive than DRAM. The costs to manufacture DRAM are about one-eighth the cost of manufacturing a comparable SRAM circuit.
As a result of this price difference, SRAMs are most commonly used where speed is required over cost, while dynamic RAM is mostly used where large amounts of data need to be stored in a cost-efficient fashion. Most hard drives use DRAM, as a result.
Without Robert Dennard’s DRAM circuits, modern computers as we know them today would simply not exist. DRAM components are used in consumer home PCs and in industry-level supercomputers. Data storage would be very different without DRAM, and probably a lot more expensive. DRAM allows for the storage of lots of information in a way that’s just not possible with other forms of memory storage.
We can expect to see continued innovation in the area of computer memory storage. Maybe someday someone will invent a form of similarly inexpensive and fast memory storage that doesn’t have the power drain caused by DRAM’s need to be refreshed. For now, however, it’s the most effective form of memory we have.
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