page_title: Dynamic random-access memory
section_title: Pseudostatic RAM (PSRAM)
hierarchical_section_title: Dynamic random-access memory / Versions / Pseudostatic RAM (PSRAM)
caption_attribution_description: English: Olivetti JP90 - Toshiba TC518129CFWL-80 (1 Mbit high speed CMOS pseudo static RAM) on controller
context_page_description: Dynamic random-access memory is a type of random access semiconductor memory that stores each bit of data in a memory cell consisting of a tiny capacitor and a transistor, both typically based on metal-oxide-semiconductor technology. The capacitor can either be charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1. The electric charge on the capacitors slowly leaks off, so without intervention the data on the chip would soon be lost. To prevent this, DRAM requires an external memory refresh circuit which periodically rewrites the data in the capacitors, restoring them to their original charge. This refresh process is the defining characteristic of dynamic random-access memory, in contrast to static random-access memory which does not require data to be refreshed. Unlike flash memory, DRAM is volatile memory, since it loses its data quickly when power is removed. However, DRAM does exhibit limited data remanence.
  DRAM typically takes the form of an integrated circuit chip, which can consist of dozens to billions of DRAM memory cells.
context_section_description: PSRAM or PSDRAM is dynamic RAM with built-in refresh and address-control circuitry to make it behave similarly to static RAM (SRAM). It combines the high density of DRAM with the ease of use of true SRAM. PSRAM (made by Numonyx) is used in the Apple iPhone and other embedded systems such as XFlar Platform.
  Some DRAM components have a "self-refresh mode". While this involves much of the same logic that is needed for pseudo-static operation, this mode is often equivalent to a standby mode. It is provided primarily to allow a system to suspend operation of its DRAM controller to save power without losing data stored in DRAM, rather than to allow operation without a separate DRAM controller as is the case with PSRAM.
  An embedded variant of PSRAM was sold by MoSys under the name 1T-SRAM. It is a set of small DRAM banks with an SRAM cache in front to make it behave much like SRAM. It is used in Nintendo GameCube and Wii video game consoles.
caption: 1 Mbit high speed CMOS pseudo static RAM, made by Toshiba
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