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RAM
Random access memory. A data storage device for which the order of access to different locations does not affect the speed of access, except for bursts. Data is typically stored in RAM temporarily for use by the process or while the computer is operating. FPM, EDO, SDRAM, DDR, etc. are all types of RAM.

Rambus
Direct Rambus is a high-speed memory technology that uses a narrow 16-bit bus (Rambus channel) to transmit data at speeds up to 800MHz.

RAS
Row address strobe. The signal that tells the DRAM to accept the given address as a row address. Used with CAS and a column address to select a bit within the DRAM.

RDRAM
Rambus DRAM is a revolutionary type of DRAM that uses a 16-18 bit data path and is designed to operate with FSB speed of 800MHz, producing a burst transfer rate of 1.6 gigahertz.

ReadyBoost
Ready Boost is a disk caching technology first included with Microsoft's Windows Vista operating system. It aims to make computers running Windows Vista more responsive by using flash memory on a USB 2.0 drive, SD card, CompactFlash, or other form of flash memory, in order to boost system performance.

Ready Boost is also used to facilitate SuperFetch, an updated version of Windows XP's prefetcher which performs analysis of boot-time disk usage patterns and creates a cache which is used in subsequent system boots.

Read Time
The amount of time required for the output data to become valid once the read and address inputs have been enabled. Generally called access time.

Reduced-Size MultiMediaCard
MMCs also come in a smaller form factor, of about half the size: 24 mm × 18 mm × 1.4 mm. This alternate form factor is known as Reduced-Size MultiMediaCard, or RS-MMC. RS-MMCs are simply smaller MMCs; by using a simple mechanical adapter to elongate the card, an RS-MMC can be used in any MMC (or SD) slot. RS-MMCs are currently available in sizes up to and including 2 GB.

Refresh
The process used to restore the charge in DRAM cells at specific intervals.

Refresh Rate
A count of the number of rows (in thousands) refreshed at a time in a refresh cycle. Common refresh rates are 1K, 2K, 4K, and 8K.

Registered Memory
Registers delay memory information for one clock cycle to ensure all communication from the chipset is collected by the clock edge, providing a controlled delay on heavily loaded memories.

RIMM
Rambus inline memory modules used for Rambus DRAM.

RoHS
The RoHS Directive stands for "the restriction of the use of certain hazardous substances in electrical and electronic equipment". This Directive bans the placing on the EU market of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants.

Row
Part of the RAM array; a bit can be stored where a column and a row intersect. Sometimes also referred to as a page.