Memoria (RAM)

MEMORIA (RAM)

Miguel A. Guillermo Castillo

Prof.Ruddy

IMPORTANT TERMS

Parity checking

Error correcting code (ECC)

Single and double sided memory

Single, double, triple channel memories

PARITY CHECKING

Parity checking is rudimentary error checking scheme that offers no error correction. Parity checking works more on a byte or 8 bit

ERROR CORRECTING CODE (ECC)

The next step in the evolution of memory error detection is know as error correction code. If the memory (RAM) supports ECC, check bits are generated and stored with the data.

SINGLE AND DOUBLE SIDED MEMORY

Commonly speaking, the term single sided memory and double sided memory refers to how some memory modules have chips on one side while others chips have on both sides. Double sided memory is essentially treated by the system as two separate memory modules

SINGLE, DOUBLE, TRIPLE CHANNEL MEMORIES

Standard memory controller manage access to memory in chunks of the same size as the system bus’s data width. This is considered communicating over a single channel. Most modern processors have 64-bit system data bus.

TYPES OF MEMORIES

DRAM

SRAM

ROM

DRAM

DRAM is Dynamic Radom Access Memory. When you expand the memory in a computer, you are adding DRAM chips. Dynamic RAM chips are cheaper to manufacture than most others types because they are less complex.

ASYNCHRONOUS DRAM

Asynchronous DRAM(ADRAM) is characterized by its independence from the CPU’s external clock. ADRAM chips have codes on them that end in a numerical value that is related to (often 1/10 of the actual value of) the access time of the memory

SYNCHRONOUS DRAM

SDRAM shares a common clock signal with the computer’s system bus clock, which provides the common signal that all local-bus components use for each step that they perform.

SDR SDRAM

With SDR SDRAM, every time the system clock ticks, 1 bit of data can be transmitted per data pin, limiting the bit rate per pin of SDRAM to the corresponding numerical value of the clock’s frequency.

SDR DDR

DDR stand for Double Data Rate SDRAM, earns its name by doubling the transfer rate of ordinary SDRAM; it does so by double –pumping the data, which means transferring a bit per pin on both the rising and falling edges of the clock signals. The data rate is1600MBos.

Volt. 2.5

182 pin

SDR DDR2

Think of the 2 in DDR2 as yet another multiplier of 2 in the SDRAM technology, using a lower peak voltage to keep power consumption down(1.8 vs. 2.5 of DDR). DDR2 using a 100MHz actual clock, transfers data in four operation per clycle(effective 400 MHz FSB) so data transfer rate is 3200MBps.

240 pin

Volt 1.8

SDR DDR3

Next generation of memory devices was designed to roughly double the performance of DDR2 products. The most commonly found range of actual clock speeds for DDR3 tends to be from 133MHz at the low end to less than 300MHz.

240 pins

Volt 1.5

SRAM

Static random access memory (SRAM)doesn’t require a refresh signal like DRAM does. The chips are more complex and are more expensive.

ROM

ROM stands for read-only memory. It is called ROM because the original form of this memory could not be written. Some form of ROM is normally used to the computer’s BIOS because this information normally does not change very often

MEMORY PACKAGING

DIMM

RIM

SODIMM

MicroDIMM

DIMM

DIIM stands for dual inline memory module. One type of memory package is known as a DIMM. DIMM are 64—bit memory modules that are used as a package for the sSDRAM family: SDR, DDR, DRR2, and DRR3.

RIMM

Assumed to stand for Rambus inline memory module but not really an acronym, RIMM is a trademark of Rambus Inc.

184 pins

SODIMM

Notebook computers and other computers that require much smaller components don't use standard RAM packages, such as the DIMM.

144 pins

MICRODIMM

A newer, smaller, and rarer RAM form factor is the microDIMM is an extremely small RAM form factor. In fact, it is over 50 percent smaller than a SODIMM..

Tiene 172 pins

REFERENCIA

Sybex CompTIA A+ 220-801, Cap:1, Pag. 35-51

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