Memory and Storage

Registered DIMM (RDIMM)

A DIMM with improved reliability. Uses a hardware register that buffers the control signals (not the application data) to the modules. The buffering adds a clock cycle and uses more power but handles the heavier electrical loads placed on high-speed, high-density memory modules better than the traditional DIMM. Suitable choice for a high-end server.

DVD-RAM

A blank DVD on which data, including music and movies, can be permanently recorded and read. These discs can be recorded over many times, but will only play back in a ____ drive.

DDR2

Twice the bus clock speed of DDR. Has between 144-200 pins.

Electrically Erasable Programmable Read-Only Memory (EEPROM) a.k.a Double-EPROM

-A type of PROM that can be erased by exposing it to an electrical current. -Requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster. -A.K.A. Each and Every PROM.

Static RAM (SRAM)

-Maintains data without constant refreshing. -Very expensive but very fast. More expensive in comparison to Dynamic Random Access Memory (DRAM). -Often used in processor cache. Utilized CPU cache memory chips.

RAID 0

-Optimized for speed and performance. Ideal for gamers. -Works with striping: data is split between two disks 50/50. Trouble is if one of the disks dies then half the data is lost.

Buffered Memory

-Also known as registered memory. -Costs more -Recommended for servers and workstations. -One clock cycle fewer. -More stability and reliability. - Less electrical load.

Gigahertz (GHz)

A unit of measurement in a PC for alternating current (AC) or electromagnetic (EM) wave frequencies equal to 1,000,000,000 Hz (billions of cycles per second).

DDR3

-4x the bus clock speed of DDR. 204 pins. -1 notch on the module contact surface

Unbuffered Memory

-Costs less. -Recommended for home systems. -No clock cycle penalty. -Standard stability and reliability. -More electrical load.

RAID 10 (1+0)

-Has a minimum of 4 disks. -This kind of RAID will help you sleep at night because, if there's a violent thunderstorm that destroys 2 disks, then you can potentially restore the information. If you lose your striping disks then you're in trouble.

RAID 1

-Or as I like to call it the twin disk array (hence the picture). -Optimized for redundancy and mirroring. -Like RAID 0, we're using 2 disks only if one disk dies then the other disks has the information. -Not ideal for speed but for data recovery it's ideal. The only disadvantage is that you're not adding memory, it's strictly a backup.

RAID 5

-Striping + Parity. -Where the information is stored amongst 3 disks minimum. -If one disk goes down then you can reconstruct the data on the third drive based on the data from the other two. -You get the speed and redundancy but it may not be cost effective.

DDR (Double Data Rate SDRAM)

-Twice the data rate of SDRAM. Transfers data on both the rising and falling edges of the clock signal. -Has 184 contact pins. -Reads/writes 2 words of data per clock cycle.

Dynamic RAM (DRAM)

-Volatile storage media type that requires constant refreshing to maintain dataWrite once. -Slower than Static Random Access Memory (SRAM). -Widely used as system's primary storage media (regular RAM modules installed in memory slots on the motherboard). -Less expensive in comparison to Static Random Access Memory (SRAM).

Non-volatile Random Access Memory (NVRAM)

A combination of RAM and EEPROM. When the machine is turned off, the data from the RAM is stored in the EEPROM. When the machine is powered on again, the data goes back to the RAM.

CD-ROM/CD-R

A compact disc used as a read-only optical memory device for a computer system. Less than 800 MB of data storage capacity. Up to 80 minutes of uncompressed audio. Can only be written once. Can record around 50x (7.5 MB/s).

Erasable and Programmable Read Only Memory (EPROM) a.k.a. UVROM

A memory chip on which data can be erased (via UV light) and rewritten. This chip can be updated without removing the BIOS chip from the motherboard.

Programmable Read Only Memory (PROM)

A memory chip on which data can only be written once.

MicroDIMM

A memory module with ~50 % higher bit density which requires ~35 % less board-space than the SO-DIMM at the same memory density. Ideal for sub-notebook devices (i.e. MacBook Air). Uses 172-214 pins.

DVD-ROM

A new type of read-only compact disc that can hold a minimum of 4.7GB (gigabytes), enough for a full-length movie.

SODIMM (small outline dual in-line memory module)

Commonly found in laptops, it is a type of computer memory built using integrated circuits. 200 pins.

Write Only Read Many (WORM)

Describes a data storage device in which information, once written, cannot be modified. This write protection affords the assurance that the data cannot be tampered with once it is written to the device. A Blu Ray disc recordable (BD-R) is an example of this.

Meghaertz (MHz)

One million cycles per second. It is used to measure the transmission speed of electronic devices, including channels, buses and the computer's internal clock.

Video RAM (VRAM)

Special-purpose memory used by video adapters and graphics controllers. Unlike conventional RAM, this type of RAM can be accessed simultaneously. Yields better graphics performance but is more expensive than normal RAM.

Synchronous Dynamic RAM (SDRAM)

Synchronizes with the clock speed that the microprocessor is optimized for. This tends to increase the number of instructions that the processor can perform in a given time.

Clock Cycles (or clock speed)

The speed at which a microprocessor or CPU executes instructions measured in MHz or GHz. The faster the _______, the more instructions the CPU can execute per second.