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SolutionBase: Sorting out the differences in program RAM With the proliferation various types of RAM available for computer systems today, it's next to impossible to keep in mind all of the different memory kinds you can choose from. Here's a quick instructions on what's available and how to let them know apart.

it's next to impossible to keep in mind all of the different memory kinds you can choose from. Here's a quick instructions on what's available and how to let them know apart.

Through the years, IT pros have seen various technologies come and go¡ªand some that just stubbornly refuse to die (floppy turns, anyone? ). One area that is changed drastically over the years is actually memory. From SIMMs in order to DIMMs to EDO to be able to Rambus, RAM has are available in all shapes and sizes and is definitely not the "one size fits all" venture. In this article, I'll check out the different kinds of RAM which has made its way in to systems over the years. If you find any stick of RAM lounging somewhere in a drawer, or even need to understand just what can make DDR and DDR2 MEMORY different, you'll have a reference.

Conditions you should know
Before embarking on some sort of memory discussion, you should be aware of the few terms that will appear during your reading to make it easier to follow along with:

Parity: With parity memory space, a bit is added to an information stream to check for mistake during the transmission. This additional bit results in parity-enabled RAM MEMORY being slightly larger than non-parity RAM. For example , a 128MB RAM module with parity actually has 144MB associated with RAM onboard to support this particular extra parity bit.
ECC (Error Checking and Correction): ECC is a type of parity checking in which a bit will be added to a data stream to check on for errors. While this could cause a very small performance strike, it increases the overall dependability of the system.
Non-parity: Generally used in lower end applications (i. e. not servers), non-parity RAM (meaning without parity and without ECC) does not perform additional error looking into data passing through the component.
Buffered: RAM with a barrier can be useful in systems having a large amount of RAM as it provides a buffer area to aid with data transmission for you to and from the chip.
CALAMIT¨¦ (Column Access Strobe): The actual CAS value is just a elegant way of asking how many program clock cycles the RANDOM ACCESS MEMORY controller waits before this puts the data on the storage bus before sending a sign that the memory can be go through. A lower CAS value indicates there is a shorter wait, leading to faster memory access.
Wait around states: One aspect of old memory technology that is eliminated from newer memory kinds is the "wait state". Prior to the advent of SDRAM, which operates at speeds synchronous to that particular of the system, RAM had been asynchronous, meaning that it went at a different speed, frequently slower than the system. This particular meant that the system needed to insert "wait states" in to the RAM access cycle to support this mismatch in time. As you can probably imagine, this specific resulted in a performance struck since these wait says were just filler. Occasionally referred to as the "access time", these performance hits might range anywhere from 40 to help 120 nanoseconds.
Registered: Authorized RAM delays information delivered from RAM by a time clock cycle, allowing RAM segments of a larger capacity to become installed in the system. The particular trade-off is performance, but as unregistered RAM will not impose this delay.
SIMM (Single Inline Memory Module)
An older type of RAM which you won't find in today's Personal computers is the SIMM, short with regard to Single Inline Memory Component. SIMMs come in two primary varieties: 30-pin and 72-pin flavors. A "pin" is among the gold- or tin-plated fittings that makes electrical contact with a new corresponding pin in the recollection slot. Regarding this bail material: don't mix all of them. If you have an older computer and they are adding RAM, don't place tin-plated sticks of GOOD OLD RAM into a gold-plated slot. Combining the metals like this helps to ensure profound results for the metal to rust and ruin both your MEMORY and possibly your motherboard.

SIMMs are notched on one part so you can quickly tell by which direction the module must be installed in the slot. The 72-pin SIMM is about four. 25" wide and about 1" tall, but the elevation can vary between vendors.

72-pin SIMMs use a 32-bit information path (36-bit for quests that support error checking) to transfer data between RAM and the system through which they're installed. 30-pin SIMMs have an 8-bit data route (9-bit for ones that assistance parity).

A 30-pin SIMM uses 5V of electrical power while a 72-pin element uses either 3. 3V or 5V. 30-pin themes come in sizes up to 8MB while 72-pin varieties could be as large as 32MB.

Number A

Notice the notch with this 30-pin SIMM. It helps to help align the module in the RAM MEMORY slot. Also notice that the amount of chips on the module is usually even, indicating non-parity RANDOM ACCESS MEMORY.
Figure B

The number of potato chips on the module is unusual, indicating a parity problem checking module.
Figure D

Notice the notch on this 72-pin SIMM. It helps to align the actual module in the RAM port. The notch in the middle differs depending on the voltage of the component. This helps to prevent damage through preventing the wrong voltage element from being used on a panel.
DIMM (Dual Inline Memory space Module)
DIMMs were the successor to SIMMs and also have 168 pins across the bottom part of the RAM stick, along with 84 on each side. DIMMs operate using a 64-bit info path, resulting in twice the entire throughput of older SIMMs. DIMMs have two steps along the bottom of the attach order to assist with properly orienting the stick in the ram slot.

Figure D

Any 168-pin DIMM has steps on either side as well as 84 pins across each party of the bottom of the component. The bottom notches determine the particular voltage of the module. This specific module is non-error-correcting because it has an even number of debris.
Figure E

This 168-pin DIMM is almost identical towards the one above, but functions error correction, as confirmed by the odd number of poker chips (usually divisible by 3).
SO-DIMM (Small Outline DIMM)

One type of DIMM which is common in laptops may be the SO-DIMM, the Small Outline RAM. Named because of it's smaller sized size (2. 66" broad for the 144 pin range used in today's laptops or perhaps 2 . 35" wide for your 72-pin SO-DIMM RAM utilized in older machines), a SO-DIMM has a small notch across the bottom of the stick to assist you to orient the chip. While DIMMs are usually installed in a right-angle to the system table, SO-DIMMs are usually installed into the angle to help save space within the system, which is useful in little spaces such as laptop instances. SDRAM SO-DIMMs run on three. 3V of electricity.

MicroDIMM

Available in 144-pin SDRAM and also 172-pin DDR (see below) varieties, a MicroDIMM is definitely smaller than a SO-DIMM. Just 1 . 50" across, a good SDRAM MicroDIMM consumes a few. 3V of latency along with pushes 2 . 1GBps of information through. The 172-pin DDR variety uses 2 . 5V.

DDR2 (see below) MicroDIMMs with 214 pins will also be making their way to the memory marketplace and require 1 . 8V of electricity.

Figure Farrenheit


A 144 pin MicroDIMM used in some notebook computers.
RIMM - Rambus Inline Storage Module
Along the way, some merchant proprietary memory modules have discovered their way into a few PCs and servers. The main culprit in this realm will be the RIMM, or Rambus Inline Memory Module. RIMMs had been developed by Rambus, often inside the news as a result of their amazing RAM.

RIMMs have 184 pins along the bottom from the circuit board, with ninety two pins on each side in the board. Rambus modules make use of a 2-byte data channel which supports transfers of up to one 6 GB per 2nd. That's pretty darn fast, even though newer types of DIMMs possess paved the way to faster memory space types. RIMMs architecture would not lend itself to a low-heat operation. In fact , if you look at any Rambus memory stick, you will notice a blue bit of metal covers all of the cash. This metal isn't just to help make the chip look cool; it can to keep it cool. Rambus memory generates a lot of temperature and the blue metal helps you to diffuse that heat.

Physique G


Rambus RIMM web template modules have heat spreaders in the individual chips.
SO-RIMM (Small Outline RIMM)

Like their own DIMM counterparts, RIMM segments have a smaller small describe companion. In this case, RIMM's is known as a SO-RIMM. Sporting one hundred sixty pins (80 on each side), a SO-RIMM is good for use within tight spaces. The smaller SO-RIMM also has the blue metallic heat spreader to help keep typically the chip cool enough to work.

Memory types
The previous 3 headings covered specific storage form factors, but did not talk too much about the method the RAM actually works. The next sections go over the different types of RAM you might find in your method.

FPM (Fast Page Mode)

After older SIMMs required hold, engineers started to enhance them. One such improved led to FPM¡ªFast Page Mode¡ªRAM. Unlike its name, FPM RAM is not considered fast! FPM GOOD OLD RAM is not suitable on techniques with a bus speed of more than 66MHz. Some older DIMMs also support FPM. These types of DIMMs run FPM utilizing either 3. 3V or maybe 5V of electricity. Typically the notch at the bottom of the element determines the voltage. Some sort of 5V module's notch will not along with a 3. 3V recollection slot, for example.

EDO (Extended Data Out)

EDO SIMMs were a technology installed just after FPM RAM. EDO RAM was still SIMM-based technologies, but allowed a ram operation to begin just before the final operation was complete, creating small performance improvement more than FPM RAM.

For quite some time, EDO was the memory of choice within systems, until the advent of often the DIMM¡ªDDR RAM in particular. EDO requires support from the anatomy's chipset and won't function without this support. Even though EDO RAM does happen to operate in a non-EDO system, it will not be able to use its more recent features, such as being able to start an operation before completing the very last.

Some older DIMMs additionally support EDO. These DIMMs run EDO using possibly 3. 3V or 5V of electricity. The level at the bottom of the module decides the voltage. A 5V module's notch won't together with a 3. 3V memory position, for example.

SDRAM (Synchronous Powerful RAM)

A newer kind of RAM, SDRAM looks almost similar to an older generic RAM, but provides faster access of data from the fewer MEMORY chips on the memory stay. SDRAM sticks still have 168 pins for the memory slot machine connect, with 84 on each of your side. The "synchronous" section of the SDRAM name helps keep the actual memory in sync using the system processor, resulting in a quicker rate of data transfer compared to that afforded by more mature types of RAM.

The list beneath provides details about the three typical types of SDRAM as teaches you the clock speed and the data rate afford by every module.

PC66: 66 MHz, 528MB/s
PC100: 100MHz, 800MB/s
PC133: 133MHz, 1 . one GB/s
168-pin SDRAM quests operate at 3. 3V or 5V.

DDR SD RAM (Double Data Rate SDRAM)

One of the newest additions to the particular DIMM class is the DDR module. DDR RAM is rather standard in today's desktop in addition to server computers, although DDR2 SDRAM (explained later) is actually beginning to show up in some devices.

DDR RAM modules can handle handling two operations for each clock cycle¡ªtwice that amount of operations as older kinds of SDRAM. This helps to explain wherever DDR gets its name.

DDR SDRAM looks similar to regular SDRAM, except it has 184 pins used for the mainboard connection and has two steps on each side of the component. The notch along the base of the module in a DDR module is also slightly different through those for other RAM modules and there is only once this kind of notch present on a DDR module.

A DDR element is similar in size to an elderly SDRAM module at around 5. 25" wide as well as 1 . 25" in height, even though height may vary depending on producer. Only memory slots upon motherboards designed specifically for DDR RAM will accept a DDR module as a result. DDR SD RAM, like other SDRAM, furthermore uses a 64-bit data tour bus to deliver data to the major system. DDR RAM works using 2 . 5V regarding electricity.

There are a number of types of DDR SDRAM on the market. Their email list below shows the name through which many companies market the product and also explains what these rankings mean. Not all of these rates of speed are "official". That is, there is not necessarily chipset support for a few of the really fast DDR speeds, although fans involving overclocking have managed to get a few of these performance numbers and some suppliers do sell memory themes at the higher speeds for the hobbyists. DDR is capable connected with providing dual data stations, resulting in twice the memory space throughput.

The math for DDR RAM goes like this:

Time clock speed * 8 octet per second (a 64-bit data path is eight bytes) = transfer pace

For example , DDR 266 (PC2100) has a clock speed associated with 266, 000 Hz (266 MHz) * 8 octet = 2, 128, 000 Bps or about second . 1 GB/s.

Other DDR Speeds include:

DDR200/PC1600: 1 ) 6 GB/s transfer snabel-a 200MHz
DDR266/PC2100: 2 . a single GB/s transfer @ 266Mhz
DDR333/PC2700: 2 . 7 GB/s transfer @ 333Mhz
DDR400/PC3200: 3. 2 GB/s move @ 400Mhz. (a large amount of literature lists this since the fastest DDR RAM available)
DDR433/PC3500: 3. 5 GB/s transfer @ 433Mhz
DDR466/PC3700: 3. 7 GB/s exchange @ 466Mhz
DDR500/PC4000: several. 0 GB/s transfer snabel-a 500Mhz
DDR533/PC4200: 4. two GB/s transfer @ 533Mhz
Figure H


A DDR 184-pin non-ECC memory component
Figure I


An outline of your DDR 184-pin non-ECC storage module
Figure J


A plan of a DDR 184-pin ECC memory module. Notice the extra chip.
DDR2 SDRAM

Around this writing, DDR2 SDRAM will be hitting the market. DDR2 begins where DDR left away and supports frequencies regarding 400MHz, 533MHz, and 667MHz. The DDR2 form element includes additional pins not really found on DDR modules. DDR2 sports 240 pins¡ª120 for every side¡ªand runs on much less power than older DDR RAM¡ª1. 8V to be exact. This kind of results in memory that doesn't need as much power and also goes cooler. A DDR2 element is about 5. 25" large and usually around 1 . 2" high, although the height can vary.

Because of these differences, DDR2 SDRAM will not work within a DDR slot. Further, the device chipset must include help for DDR2 RAM.

Such as DDR, DDR2 SDRAM sports activities a 64-bit data journey, or 72-bits wide regarding registered or ECC recollection modules. Further, DDR2 RAM can make use of dual files channels, with appropriate chip-set support, providing a 128-bit records path to the system, resulting in enhanced RAM performance.

The list under outlines the three major DDR2 classes. Expect more to become added a la DDR.

DDR2-400/PC2-3200: 3. 2GB/s @ 400MHz (6. 4GB/s with double channels enabled)
DDR2-533/PC2-4200: some. 2GB/s @ 533MHz (8. 4GB/s with dual programmes enabled)
DDR2-667/PC2-5300: 5. 3GB/s @ 667MHz (10. 6GB/s with dual channels enabled)
Figure K


This ram module is a DDR2 non-ECC module as evidenced through the even number of chips within the module.
Figure L


That memory module is a DDR2 Registered ECC module because evidenced by the odd quantity of chips on the module.
DDR SO-DIMM (DDR Small Describe DIMM)

By now, you know that this SO part of a DDR SO-DIMM means that it's a tiny outline form factor utilized most in laptop computers along with other small devices. Other than actual physical size, the other primary distinction between a DDR RAM and a DDR SO-DIMM could be the number of pins that link the stick to the motherboard. A new DDR SO-DIMM has two hundred such connections¡ª100 on each aspect. DDR and DDR2 SO-DIMMs measure about 2 . 66" wide and 1 . 25" tall.

Figure M


This particular memory module is a DDR-SODIMM module with 200 complete pins.
Determining memory kind by sight
This is a difficult section to write as there are numerous variables and some RAM producers have opted to not print out anything on a memory component, making it very difficult to completely determine.

I've already provided several ways throughout the article that you could quickly identify modules simply by sight. However , all these suggestions tell you is the overall kind of RAM present in the system¡ªi. e. DDR, SIMM, and so on You might want to try to be able to inform if the RAM you're keeping is a 256MB stick or perhaps a 1GB stick, or be it ECC-enabled or might be authorized. Here are some tips I've collected coming from all over the place to help you in your recognition efforts.

Module size: For those who have a lot of RAM to identify, save this site. It provides information concerning a number of manufacturers and their RAM MEMORY numbering methods. Unfortunately, each and every manufacturer uses a different numbering scheme, so it's extremely difficult to see how large a module is simply by looking. If you can manage to work out how large each of the individual potato chips is (sometimes the part quantity on the chip will give that away), multiply that dimension by the number of chips around the board. If the number of debris is divisible by about three, subtract one from the overall count as the last nick does not hold data; is actually used for error checking.
Parity/ECC: Count the number of same-sized poker chips on your RAM module. When the number is divisible by simply 3 (or sometimes 5), the module support both parity or ECC fault checking. If the module's computer chip count is not divisible by means of 3, you have non-parity RANDOM ACCESS MEMORY.
Buffered: I've read that will buffered RAM can be recognized by determining whether the prospects next to first notch tend to be evenly spaced.
Registered: In case you memory module has an further chip near the memory cash, it might be registered memory.
Keeping in mind memory facts
As you can most likely tell, there have been a number of different forms of RAM through the years. This is don't ever intended to be a 100% total guide to all things memory associated. To compile such a manual would simply require a lot of space to be usable. Rather, this is intended to provide a fast overview to some of the web template modules you might run across and efforts to help you identify what you curently have on hand.

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