DRAM

Invented by : Robert H. Dennard & Intel

Invented in year : 1968

DRAM is an abbreviated form which stands for Dynamic Random Access Memory. The network of electrically-charged points in which a computer stores quickly accessible data in the form of 0s and 1s is called memory. Random access means that the PC processor can access any part of the memory directly rather than having to proceed sequentially from some starting place. DRAM is dynamic in that, unlike static RAM (SRAM), it needs to have its storage cells refreshed or given a new electronic charge every few milliseconds. Static RAM does not need refreshing because it operates on the principle of moving current that is switched in one of two directions rather than a storage cell that holds a charge in place. Static RAM is generally used for cache memory, which can be accessed more quickly than DRAM.
DRAM stores each bit in a storage cell consisting of a capacitor and a transistor. Capacitors tend to lose their charge rather quickly; thus, the need for recharging.

Brief History

In 1964, Arnold Farber and Eugene Schlig working for IBM created a memory cell that was hard wired; using a transistor gate and tunnel diode latch, they later replaced the latch with two transistors and two resistors, which became known as the Farber-Schlig cell. In 1965, Benjamin Agusta and his team working for IBM managed to create a 16-bit silicon memory chip based on the Farber-Schlig cell which consisted of 80 transistors, 64 resistors and 4 diodes.

Dr. Robert H. Dennard, a Fellow at the IBM Thomas J. Watson Research Center created the one-transistor DRAM in 1966. Dennard and his team were working on early field-effect transistors and integrated circuits and his attention to memory chips came from seeing another team's research with thin-flim magnetic memory. Dennard claims he went home and within a few hours had gotten the basic ideas for the creation of DRAM. He worked on his ideas for a simpler memory cell that used only a single transistor and a small capacitor. IBM and Dennard were granted patent number 3,387,286 for DRAM in 1968.

Development in the invention of DRAM

In 1969 Honeywell (major conglomerate company dealing in electronics etc.) asked Intel to make a DRAM using a 3-transistor cell that they had developed. This became the Intel 1102 (1024x1) in early 1970.

However the 1102 had many problems, prompting Intel to begin work on their own improved design (in secrecy to avoid conflict with Honeywell). Thus in October 1970, Intel developed the first commercially-available DRAM, known as the i1103.

In 1971, Intel releases the 1101 chip, a 256-bit programmable memory, and the 1701 chip, a 256-byte erasable read-only memory (EROM). In 1973, the first DRAM with multiplexed row and column address lines was introduced . It was known as the Mostek MK4096 (4096x1). This addressing scheme, a radical advance, allowed it to fit into packages with fewer pins, a cost advantage that would grow with every jump in memory size.

In 1997, SD RAM appeared on the market. SD RAM was an alternative to DRAM and SRAM. It was able to run at a faster clock rate. As a result of a much simpler communication mode, that SD RAM employs, all commands, addresses, and data are timed to a single clock signal. SD RAM is a burst mode memory that bursts a series of data words at the 66-MHz clock rate following the initial 58-ns random access latency. The typical organization of the memory modules changed from the single in-line memory module (SIMM) to the dual in-line memory module (DIMM) that supported the entire 64-bit databus width with a single module.

In 1998, the SD RAM frequency had increased to a 100-MHz burst rate. The random access latency improved to 56 ns. Both processor clock speed and memory bandwidth had increased by 12 times, but the DRAM latency in clock cycles had become more than 5 times worse. Computer system performance started to become limited by latency and not by bandwidth.

In 1999, corporate competition between Intel and AMD increased and so did the CPU clock speed. Unfortunately, this rapid development in the processor industry, created a further widening of the cleft between CPU clock speed and the rest of the system components. This led to the increase in memory bus speed to 133 MHz. Yet, the chipset still suffered from latency problems.

During 2000, DDR RAM (double data rate transfer) was introduced in order to deal with latency problem. AMD is the first company to use DDR RAM in their motherboard. DDR RAM allows for data to be fetched on both the rising and falling edges of the clock, thus doubling the effective transfer rate of the clock. For example, a 100-MHz DDR clock would achieve a peak transfer rate equal to that of a 200-MHz clock. The effective transfer rate is equal to the clock frequency multiplied by the bus width, doubled.

In the second quarter of 2003, DDR2 was introduced as result of improvement in DDR technology. It offered a substantial performance increase over traditional DDR memory. As of 2009, DDR3, which offers improvements over DDR2, is being implemented into the fastest computers and laptops.

Role of the Invention of DRAM in the improvement of human life

• DRAM composed of  simple structure. It had only one transistor and a capacitor are required per bit, compared to four transistors in SRAM. This allows DRAM to reach very high density. Unlike flash memory, it is volatile memory (cf. non-volatile memory), since it loses its data when the power supply is removed.

• It became the standard of the industry for RAM and enabled the microcomputer revolution. It is now commonly used in all forms of business and personal computers.