Search results
Results from the WOW.Com Content Network
RAS only refresh – In this mode the address of the row to refresh is provided by the address bus lines typically generated by external counters in the memory controller. CAS before RAS refresh (CBR) – In this mode the on-chip counter keeps track of the row to be refreshed and the external circuit merely initiates the refresh cycles. [5]
SDRAM designed for battery-powered devices offers some additional power-saving options. One is temperature-dependent refresh; an on-chip temperature sensor reduces the refresh rate at lower temperatures, rather than always running it at the worst-case rate. Another is selective refresh, which limits self-refresh to a portion of the DRAM array.
If RAS is then asserted again, this performs a CBR refresh cycle while the DRAM outputs remain valid. Because data output is not interrupted, this is known as hidden refresh. [61] Hidden refresh is no faster than a normal read followed by a normal refresh, but does maintain the data output valid during the refresh cycle.
A memory controller, also known as memory chip controller (MCC) or a memory controller unit (MCU), is a digital circuit that manages the flow of data going to and from a computer's main memory. [ 1 ] [ 2 ] When a memory controller is integrated into another chip, such as an integral part of a microprocessor , it is usually called an integrated ...
The time to read the first bit of memory from a DRAM with the wrong row open is T RP + T RCD + CL. Row Active Time T RAS: The minimum number of clock cycles required between a row active command and issuing the precharge command. This is the time needed to internally refresh the row, and overlaps with T RCD. In SDRAM modules, it is simply T RCD ...
The 825x chips, or an equivalent circuit embedded in a larger chip, are found in all IBM PC compatibles and Soviet computers like the Vector-06C. In PC compatibles, Timer Channel 0 is assigned to IRQ-0 (the highest priority hardware interrupt). Timer Channel 1 is assigned to DRAM refresh (at least in early models before the 80386).
A second type, DRAM (dynamic RAM), is based on MOS capacitors. Charging and discharging a capacitor can store either a '1' or a '0' in the cell. However, since the charge in the capacitor slowly dissipates, it must be refreshed periodically. Due to this refresh process, DRAM consumes more power, but it can achieve higher storage densities.
Circuit board design: [52] New power supplies (VDD/VDDQ at 1.2 V and wordline boost, known as VPP, at 2.5 V); VrefDQ must be supplied internal to the DRAM while VrefCA is supplied externally from the board; DQ pins terminate high using pseudo-open-drain I/O (this differs from the CA pins in DDR3 which are center-tapped to VTT). [52]