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Comparison of Two Random Access Memory Products


Introduction

The following report is a comparison of DDR memory available on the commercial market today. The two selected products are available from Novatech, and other supplies such as Amazon, ebuyer and PC world.
DDR (Double Data Rate) memory was the successor or SDRAM (Synchronous Dynamic Random-Access Memory). It was first released in 1991. DDR memory is not forward compatible and is no longer manufactured as it is now succeeded by DDR2 and DDR3. The latter two, are later versions with faster access times and lower power consumption.
DDR3 memory was first release in 2007. DDR3 memory is not backward compatible due to signalling voltages, pinout and timings. This memory type is currently in use today.
The two selected memory products for comparison are:


Comparison

Memory Size

The selected DDR memory has a memory size of one gigabyte, which was the maximum available at the time of manufacture due to physical capacity of the memory module (number of chips on the PCB).
The selected DDR3 memory has a memory size of eight gigabytes. This is the maximum available in a single module to date. DDR3 memory is available in single channel, dual channel and quad channel. Combining memory in more than one channel allows the user to increase memory size as well as performance.
The DDR3 memory has a larger capacity due to advances in silicon technology. These advances are:

Interface Speed

The interface speed comparison includes clock speed and transfer rate.
The selected DDR memory has a maximum clock speed of 400MHz but typically the clock speed will be set to 200MHz due to the way the memory is accessed and the width of the data bus. With the DDR3 memory the maximum clock speed is 1600MHz, typically 800MHz.
The maximum transfer rate of the DDR memory is 1,600MB per second, typically 400MB per second, whereas the DDR3 memory has a maximum transfer rate of 12,800MB per second, typically 1,600MB per second, i.e. the typical data transfer rate of the DDR3 memory is the same as the maximum transfer rate of the DDR memory.


Latency

Latency is the maximum time the memory controller must wait between requesting data and receiving the data.
The DDR memory has a typical latency of 3 clock cycles whereas the DDR3 memory has a typical latency of 7 clock cycles.
This appears on the surface that DDR has a quicker access time than DDR3, however because DDR3 has a much faster clock speed (as stated in interface speed) the overall data access is much faster.

Power Consumption

DDR memory requires a supply voltage of 2.5V whereas DDR3 requires a supply voltage of 1.8V.
This is a consequence of larger scale integration and smaller gate size. The result of smaller gate size is less gate capacitance and therefore less power is required to change the state of the gate. From the formula for energy stored in a capacitor E=1/2CV2 it can be seen that halving the supply voltage reduces the energy by four times: a significant saving in energy.

Architecture

The DDR memory has 184 pins whereas DDR3 has 240 pins. The increase in pins allows the memory module to communicate at a faster data rate but requires more space for the memory to be attached to the motherboard.
The DDRís memory chips are thin small-outline packages (TSOP), whereas the DDR3ís memory chips are ball grid array packages (BGA). The TSOPs require more space on a PCB than a BGA therefore more memory chips can be attached to a DDR3 memory module than that of a DDR memory module.

Cost

Today, a DDR memory module costs £16.98 whereas a DDR3 memory module will cost £44.99. The DDR module costs less because itís:
  1. Old technology and therefore not used very often;
  2. obsolete technology which is no longer used.

Conclusion

From the comparison between these two memory types it can be seen that with the advance of technology larger memory and lower power consumption will be the future. As manufactures improve silicon technology, memory density should increase and resulting power consumption savings will follow. This is an key selling point as the ecology of the planet is becoming more important.


DDR Memory:
DDR Memory

DDR3 Memory:
DDR3 Memory

Torres, G (2009, August 27). Everything You Need To Know About DDR, DDR2 and DDR3 Memories | Hardware Secrets. Retrieved May 5, 2013, from http://www.hardwaresecrets.com/printpage/Everything-You-Need-To-Know-About-DDR-DDR2-and-DDR3-Memories/167
Novatech (n.d.). Novatech 8GB (1x8GB) DDR3 PC3-12800C9 1600MHz Single Channel kit | RAM-16008. Retrieved May 5, 2013, from http://www.novatech.co.uk/products/components/memory-pc/ddr3-pc3-12800/1600mhz/ram-16008.html
Novatech (n.d.). 400MHz 184Pin 1GB PC3200 DDR RAM DIMM 2.5V 3.2Gb/Sec | RAM-40/1G. Retrieved May 5, 2013, from http://www.novatech.co.uk/products/components/memory-pc/ddr-pc2100-pc3200/266-400mhz/ram-401g.html
Wikipedia (n.d.). DDR SDRAM - Wikipedia, the free encyclopedia. Retrieved May 5, 2013, from http://en.wikipedia.org/wiki/DDR1_SDRAM
Wikipedia (n.d.). DDR3 SDRAM - Wikipedia, the free encyclopedia. Retrieved May 5, 2013, from http://en.wikipedia.org/wiki/DDR3_SDRAM
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