Memory Review

RAM, DRAM, SRAM, RDRAM, VRAM, WRAM, SIMM, DIMM, EDO, DDR-SRAM

SRAM
Static random access memory uses multiple transistors, typically four to six, for each memory cell but doesn't have a capacitor in each cell. It is used primarily for cache. Is faster than DRAM because it does not require refreshing but it is more expensive

DRAM
Dynamic random access memory has memory cells with a paired transistor and capacitor requiring constant refreshing.

FPM DRAM
Fast page mode dynamic random access memory was the original form of DRAM. It waits through the entire process of locating a bit of data by column and row and then reading the bit before it starts on the next bit. Maximum transfer rate to L2 cache is approximately 176 megabytes per second.

EDO DRAM
Extended data-out dynamic random access memory does not wait for all of the processing of the first bit before continuing to the next one. As soon as the address of the first bit is located, EDO DRAM begins looking for the next bit. It is about five percent faster than FPM. Maximum transfer rate to L2 cache is approximately 264 megabytes per second.

SDRAM
Synchronous dynamic random access memory takes advantage of the burst mode concept to greatly improve performance. It does this by staying on the row containing the requested bit and moving rapidly through the columns, reading each bit as it goes. The idea is that most of the time the data needed by the CPU will be in sequence. SDRAM is about five percent faster than EDO RAM and is the most common form in desktops today. Maximum transfer rate to L2 cache is approximately 528 megabytes per second.

RDRAM
Rambus dynamic random access memory is a radical departure from the previous DRAM architecture. Designed by Rambus, RDRAM uses a Rambus in-line memory module (RIMM), which is similar in size and pin configuration to a standard DIMM. What makes RDRAM so different is its use of a special high-speed data bus called the Rambus channel. RDRAM memory chips work in parallel to achieve a data rate of 800 MHz.

RDRAM

RDRAM is a general purpose high-performance memory device suitable for use in a broad range of applications including computer memory, graphics, video, networking and any other application where high bandwidth and low latency are required.

The use of RSL (Rambus Signaling Level) technology permits 1066MHz transfer rates while using conventional system and board design technologies. The architecture of RDRAMs allows the highest sustained bandwidth for multiple, simultaneous randomly addressed memory transactions. The separate control and data buses with independent row and column control yield over 95% bus efficiency. The RDRAM's multi-banks configuration supports up to four simultaneous transactions.

 VRAM
VideoRAM, also known as multiport dynamic random access memory (MPDRAM), is a type of RAM used specifically for video adapters or 3-D accelerators. The "multiport" part comes from the fact that VRAM normally has both random access memory and serial access memory. VRAM is located on the graphics card and comes in a variety of formats, many of which are proprietary. The amount of VRAM is a determining factor in the resolution and color depth of the display. VRAM is also used to hold graphics-specific information such as 3-D geometry data and texture maps.

WRAM

Short for Windows RAM, a type of RAM developed by Samsung Electronics that supports two ports. This enables a video adapter to fetch the contents of memory for display at the same time that new bytes are being pumped into memory. This results in much faster display than is possible with conventional single-port RAM.

WRAM is similar to VRAM, but achieves even faster performance at less cost because it supports addressing of large blocks (windows) of video memory.

SIMM

Acronym for single in-line memory module, a small circuit board that can hold a group of memorychips. Typically, SIMMs hold up 8 (on Macintoshes) or 9 (on PCs) RAM chips. On PCs, the ninth chip is often used for parity error checking. Unlike memory chips, SIMMs are measured in bytes rather than bits. SIMMs are easier to install than individual memory chips.

The bus from a SIMM to the actual memory chips is 32 bits wide. A newer technology, called dual in-line memory module (DIMM), provides a 64-bit bus. For modern Pentium microprocessors that have a 64-bit bus, you must use either DIMMs or pairs of SIMMs.

DIMM

Short for dual in-line memory module, a small circuit board that holds memorychips. A single in-line memory module (SIMM) has a 32-bit path to the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a 64-bit path to memory, you need to install SIMMs two at a time. With DIMMs, you can install memory one DIMM at a time.

EDO

Short for Extended Data Output Dynamic Random Access Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU.

 

DDR-SRAM

Short for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle (the rising and falling edges), effectively doubling the memory chip's data throughput. DDR-SDRAM also consumes less power, which makes it well-suited to notebook computers. DDR-SDRAM is also called SDRAM II.

  

MICRON WILL demonstrate its DDR-II memory at the VIA Technical Forum (VTF) in Taiwan this week. The memory runs at 533Mbit/sec. per pin and achieves system bandwidth of 4300Mbytes per second, the company says.

Micron will also show off DDR400 and DDR333 systems, but all eyes will be on its DDRII implementation.

In a statement, Micron mouthpiece, Terry Lee said: "While the industry adoption of DDR-II in high volume is not expected until late 2003 and early 2004, our customers benefit from our early system analysis work. Micron will enable our customers to effectively utilize DDR-II memory technology in the same manner as we have DDR-I."

Both Samsung an Elipda have already shown details of 512-Mbit DDRII chips, Elipda having sampled chips back in July.

http://www.theinquirer.net/?article=5743

 

System Bus

533/400 MHz (data)

400MHz (data)

533/400 MHz (data)

533/400 MHz (data)

533/400 MHz (data)

533/400 MHz (data)

533/400 MHz (data)

400MHz (data)

Memory Modules

4 RIMMs

4 RIMMs

2 double-sided DDR DIMMs

2 double-sided DDR DIMMs

2 double-sided DDR DIMMs, 2 double-sided SDR DIMMs

2 double-sided DDR DIMMs

2 double-sided DDR DIMMs or SDR DIMMs

2 double-sided DDR DIMMs, 3 double-sided SDR DIMMs

Memory Type

PC1066 PC800-40 PC800-45 RDRAM

PC800-40 PC800-45 PC600-40 RDRAM

DDR 333/266

DDR 333/266

DDR 266/200 PC133 SDRAM

DDR 266/200

DDR 266/200 PC133 SDRAM

DDR 266/200 PC133 SDRAM

FSB/Memory Configurations

533/PC1066 533/PC800-40 400/PC800-45 400/PC800-40

400/PC800-45 400/PC800-40 400/PC600-40

533/333 533/266 400/266

533/333 533/266 400/266

533/266 533/200 400/266 400/200 400/133

533/266 533/200 400/266 400/200

533/266 533/200 400/266 400/200 400/133

400/266 400/200 400/133

 

A bus allows multiple devices to communicate, as compared to an interface, which is the connection from one device to another device or bus.