Ddr Memory Slot Function
DDR SDRAM is a stack of acronyms. Double Data Rate (DDR) Synchronous Dynamic Random Access Memory (SDRAM) is a common type of memory used as RAM for most every modern processor. First on the scene of this stack of acronyms was Dynamic Random-Access Memory (DRAM), introduced in the 1970s. DRAM is not regulated by a clock. DRAM is asynchronous, i.e., not synchronized by any external influence. This posed a problem in organizing data as it comes in so it can be queued for the process it’s associated with. Because DRAM was asynchronous, it was not going to work as fast with processors that were just getting faster.
SDRAM is synchronous, and therefore relies on a clock to synchronize signals, creating predictable orderly cycles of data fetches and writes. However, SDRAM transfers data on one edge of the clock. DDR SDRAM means that this type of SDRAM fetches data on both the leading edge and the falling edge of the clock signal that regulates it, thus the name “Double Data Rate.” Prior to DDR, RAM would fetch data only once per clock cycle. Synchronous data lends itself to faster operation when coordinating memory fetches with the processor’s requirements.
Many people refer to a processor’s RAM as simply “DDR”, using the terms interchangeably because DDR is so widely used as CPU RAM and has been since the late 1990s. DDR is not flash memory like the kind that is used for Solid State Drives (SSDs), Secure Digital (SD) cards, or Universal Serial Bus (USB) drives. DDR memory is volatile, which means that it loses everything once power is removed.
Dynamic random access memory (DRAM) is a type of semiconductor memory that is typically used for the data or program code needed by a computer processor to function. DRAM is a common type of random access memory (RAM) that is used in personal computers (PCs), workstations and servers. Intel® Core™ i5 (Below) - Supports DDR4-2666 Memory (Max.) Supports Dual-Channel mode Supports non-ECC, un-buffered memory Supports Intel® Extreme Memory Profile (XMP) Expansion Slots: 1x PCIe 3.0 x16 slot (From CPU, PCIE1), supports x16 mode 1x PCIe 3.0 x16 slot (From PCH, PCIE3), supports x4 mode ¹.
This may seem like a detriment, but the trade-off is that DDR has much faster transfer rates than other memory products, as well as a high capacity. The ubiquitous use of DDR SDRAM for a processor’s working memory, or RAM, has improved over the years as the industry has progressed from DDR to DDR2, DDR3, and now DDR4 SDRAM (see Table 1). DDR2 – DDR4 evolved to require lower supply voltages, which generally saves power. Other changes were made to increase the speed, as well. DDR2 SDRAM was reduced to operating at a voltage of 1.8 volts, and a clock multiplier was added to the memory module to again double data transfer speeds while operating at the same bus speed. DDR3 RAM integrated a 4x clock multiplier, again doubling the memory transfer rate for the same bus speed.
TABLE 1: Comparison of SDRAM in order of release. Clock and transfer rates are approximate and vary by manufacturer.
| Standard (Approximate Year Introduced) | Operating Voltage | Amount of Data Transferred (Words per Clock Cycle) | Associated RAM Clock Rates | Approximate Transfer Rates |
| SDRAM (1993) | 3.3 V | 1 | 66 – 133 MHz | 100 – 166 MT/s |
| DDR SDRAM (2000) | 2.6 V, 2.5 V | 2 | 100 – 200 MHz | 200 – 400 MT/s |
| DDR2 SDRAM (2003) | 1.8 V, 1.55 V | 4 | 200 – 400 MHz | 400 – 1066 MT/s |
| DDR3 SDRAM (2007) | 1.5 V, 1.35 V | 8 | 400 MHz – 1066 MHz | 800 – 2133 MT/s |
| DDR4 SDRAM (2014) | 1.2 V | 8 | 1066 – 1600 MHz | 1600 – 3200 MT/s |
In addition to a steady decrease in operating voltage and power consumption, DDR also became denser as more transistors were packed into a smaller area. DDR SDRAM is packaged as an integrated chip module, which includes the Dual In-Line Memory Module (DIMM) used with desktop computers. DIMM is a small PCB populated with SDRAM chips. Before DIMM, we had Single In-Line Memory Modules (SIMMs), which were used in the 1980s and 1990s. DIMM chips carry DDR SDRAM for upgrading RAM on a PC.
This article discusses the more modern versions of volatile RAM, including general points on DDR SDRAM standard and how it evolved. Before DRAM, there was the also-volatile SRAM (Static Random Access Memory). The fundamental differences between DRAM and SRAM were covered in an earlier post. More on non-volatile memory can be found in an earlier post Embedded use of NAND and NOR flash memory is evolving.
DDR5 SDRAM is the next standard proposed to double the speed of DDR4 SDRAM. According to the JEDEC Solid State Technology Association, the standard-bearer for DDR SDRAM, “The JEDEC DDR5 standard is currently in development in JEDEC’s JC-42 Committee for Solid State Memories. JEDEC DDR5 will offer improved performance with greater power efficiency as compared to previous generation DRAM technologies. As planned, DDR5 will provide double the bandwidth and density over DDR4, along with delivering improved channel efficiency.” DDR5 SDRAM is forecasted for 2018.
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Alternately referred to as multi-channel memory, dual-channel memory is a DDR, DDR2, or DDR3 chipset on the motherboard providing RAM with two dedicated high-throughput data channels. The channels permit reading from and writing to memory to occur on distinct channels.
To take advantage of a dual-channel platform when purchasing memory make sure to buy memory in identical pairs. For example, if you wanted to upgrade to an additional 2 GB of memory. Buy two 1 GB memory modules that are exactly identical. While each memory chip's speed doesn't need to be the same as the others, it's best to install memory with matching speeds. If the speeds differ, the motherboard runs the memory chips at the speed of the slowest chip.
Finally, if you are only installing two memory modules at a time make sure the memory is installed into the proper memory slots. Almost always the memory slots will be color-coded to indicate the memory channel, as shown in the picture below. The first channel is often slots one and two, and the second channel is three and four. When installing memory in pairs make sure to install them into the same colored slot to take advantage of the dual-channel platform.
As can be assumed by the names, triple-channel architecture triples the available memory bandwidth and Quad-channel architecture quadruples the memory bandwidth. As with dual-channel architecture memory should be installed in a set of three or four depending on the architecture of the motherboard.
How do I know if dual-channel is active?
When active your initial boot screen that displays your memory speeds and capacity should show 'Dual Channel' or 'Dual Channel Interleaved' somewhere in the memory settings. Alternatively, software programs like CPU-Z can also detect and display this information.
I have four memory chips, do they all need to be the same?
For dual-channel, you only need to install memory in pairs. All four memory sticks do not need to be the same, only the pairs need to be the same and installed in their proper memory slots.
