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An address bus is a bus that is used to specify a physical address. When a processor or DMA-enabled device needs to read or write to a memory location, it specifies that memory location on the address bus (the value to be read or written is sent on the data bus). The width of the address bus determines the amount of memory a system can address.
The naming convention for DDR, DDR2 and DDR3 modules specifies either a maximum speed (e.g., DDR2-800) or a maximum bandwidth (e.g., PC2-6400). The speed rating (800) is not the maximum clock speed, but twice that (because of the doubled data rate). The specified bandwidth (6400) is the maximum megabytes transferred per second using a 64-bit width.
FPM, EDO, SDR, and RDRAM memory was not commonly installed in a dual-channel configuration. DDR and DDR2 memory is usually installed in single- or dual-channel configuration. DDR3 memory is installed in single-, dual-, tri-, and quad-channel configurations. Bit rates of multi-channel configurations are the product of the module bit-rate (given ...
DDR4 memory is supplied in 288-pin dual in-line memory modules (DIMMs), similar in size to 240-pin DDR3 DIMMs. DDR4 RAM modules feature pins that are spaced more closely at 0.85 mm compared to the 1.0 mm spacing in DDR3, allowing for a higher pin density within the same standard DIMM length of 133.35 mm (5¼ inches).
Setting an FSB speed is related directly to the speed grade of memory a system must use. The memory bus connects the northbridge and RAM, just as the front-side bus connects the CPU and northbridge. Often, these two buses must operate at the same frequency. Increasing the front-side bus to 450 MHz in most cases also means running the memory at ...
Double Data Rate 3 Synchronous Dynamic Random-Access Memory (DDR3 SDRAM) is a type of synchronous dynamic random-access memory (SDRAM) with a high bandwidth ("double data rate") interface, and has been in use since 2007. It is the higher-speed successor to DDR and DDR2 and predecessor to DDR4 synchronous dynamic random-access memory (SDRAM) chips.
Earlier DIMM generations featured only a single channel and one CA (Command/Address) bus controlling the whole memory module with its 64 (for non-ECC) or 72 (for ECC) data lines. Both subchannels on a DDR5 DIMM each have their own CA bus, controlling 32 bits for non-ECC memory and either 36 or 40 data lines for ECC memory, resulting in a total ...
In addition to double pumping the data bus as in DDR SDRAM (transferring data on the rising and falling edges of the bus clock signal), DDR2 allows higher bus speed and requires lower power by running the internal clock at half the speed of the data bus. The two factors combine to produce a total of four data transfers per internal clock cycle.