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In a single read or write operation, only one bank is accessed, therefore the number of bits in a column or a row, per bank and per chip, equals the memory bus width in bits (single channel). The size of a bank is further determined by the number of bits in a column and a row, per chip, multiplied by the number of chips in a bank.
The first HDD [11] had an average seek time of about 600 ms. [12] and by the middle 1970s, HDDs were available with seek times of about 25 ms. [13]Some early PC drives used a stepper motor to move the heads, and as a result had seek times as slow as 80–120 ms, but this was quickly improved by voice coil type actuation in the 1980s, reducing seek times to around 20 ms.
Also some memory controllers have a maximum supported number of ranks. DRAM load on the command/address (CA) bus can be reduced by using registered memory. [citation needed] Predating the term rank (sometimes also called row) is the use of single-sided and double-sided modules, especially with SIMMs. While most often the number of sides used to ...
The name "DIMM" was chosen as an acronym for Dual In-line Memory Module symbolizing the split in the contacts of a SIMM into two independent rows. [6] Many enhancements have occurred to the modules in the intervening years, but the word "DIMM" has remained as one of the generic terms for a computer memory module.
The physical phenomena on which the device relies (such as spinning platters in a hard drive) will also impose limits; for instance, no spinning platter shipping in 2009 saturates SATA revision 2.0 (3 Gbit/s), so moving from this 3 Gbit/s interface to USB 3.0 at 4.8 Gbit/s for one spinning drive will result in no increase in realized transfer rate.
(memory density) This is the total memory capacity of the chip. Example: 128 Mib. (memory depth) × (memory width) Memory depth is the memory density divided by memory width. Example: for a memory chip with 128 Mib capacity and 8-bit wide data bus, it can be specified as: 16 Meg × 8. Sometimes the "Mi" is dropped, as in 16×8.
Additionally, a memory management unit (MMU) is a small device between CPU and RAM recalculating the actual memory address, for example to provide an abstraction of virtual memory or other tasks. As the RAM types used for primary storage are volatile (uninitialized at start up), a computer containing only such storage would not have a source to ...
The SDRAM also maintains an internal counter, which iterates over all possible rows. The memory controller must simply issue a sufficient number of auto refresh commands (one per row, 8192 in the example we have been using) every refresh interval (t REF = 64 ms is a common value). All banks must be idle (closed, precharged) when this command is ...