get memory info.
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There are three main types of RAM today: SDRAM, DDR and DDR2.
Traditional SDRAM (Synchronous DRAM)
Almost all systems prior to 2005 used to ship with 3.3 volt, 168-pin SDRAM DIMMs. SDRAM is not an extension of older EDO DRAM but a new type of DRAM altogether. SDRAM started out running at 66 MHz, while older fast page mode DRAM and EDO max'd out at 50 MHz. SDRAM is able to scale to 133 MHz (PC133) officially, and unofficially up to 180MHz or higher. This SDRAM , around mid-to-late 2005, was inhibiting the speed at which the faster Processors were able to clock data in and out of memory. This previous generation SDRAM was becomeing the bottleneck in attaining faster system speeds.As processors got faster, new generations of memory such as DDR and RDRAM were required to get proper performance. DDRAM (Double Data Ram) evolved from the need to search out an alternative to this older style SDRAM to free up this pressing bandwidth limitation.
DDR (Double Data Rate SDRAM)
DDR basically doubles the rate of data transfer of standard SDRAM by transferring data on the up and down tick of a clock cycle. DDR memory operating at 333MHz actually operates at 166MHz * 2 (aka PC333 / PC2700) or 133MHz*2 (PC266 / PC2100). DDR is a 2.5 volt technology that uses 184 pins in its DIMMs. It is incompatible with SDRAM physically, but uses a similar parallel bus, making it easier to implement than RDRAM, which is a different technology.
DDR2
In late 2005 -2006 DDR2 became popular and improved the speed of clocking once again increasing memory speed for the even higher cpu's.
Older RAM types that are now almost obsolete
Fast Page Mode DRAM
FPM DRAM (Fast Page Mode DRAM) is plain old DRAM as we once knew it. The problem with standard FPM DRAM was that it maxes out at about 50 MHz. ( Processors these days are in excess of 533Mhz.)
EDO DRAM
EDO DRAM gave people up to 5% system performance increase over DRAM. EDO DRAM is like FPM DRAM with some cache built into the chip. Like FPM DRAM, EDO DRAM maxes out at about 50 MHz. Early on, some system makers claimed that if you used EDO DRAM you didn't need L2 cache in your computer to get decent performance. They were wrong. It turns out that EDO DRAM works along with L2 cache to make things even faster, but if you lose the L2 cache, you lose a lot of speed.
But these older types are well and truly gone as the new DDR and DDR2 RAM have blitzed them for speed.
Memory Speed
Traditional SDRAM
The traditional SDRAM initially shipped at a speed of 66MHz. As memory buses got faster, the speed was increased to
100MHz, and then 133MHz. These speed grades are referred to as PC66 (unofficially), PC100 and
PC133 SDRAM respectively.
DDR Ram
The faster DDR comes in PC1600, PC2100, PC2700 and PC3200 DIMMs. They are also often referred to as DDR200, DDR266, DDR333 and DDR400 representing the effective FSB clock speeds that they can attain.
DDR2 Ram
The evolutionary changes enable DDR2 to operate between 400 MHz and 533 MHz, extending to 667 MHz and 800 MHz. These can also be termed as PC2-4200 (DDR533) and PC2-3200 (DDR400), and so on.
What is DDR Memory?
DDR memory, or Double Data Rate memory, is a new high performance type of SDRAM memory that runsat twice the speed of previous generation SDRAM. This DDR SDRAM keeps pace with the faster clock speeds of newer processors being released and so ensuring increased overall system speed. The faster the memory, the quicker instructions can be passed to the processor. Previous generation SDRAM had become the main bottleneck in faster processor systems. DDR memory provides roughly a 15% boost in performance compared to previous generation non-DDR SDRAM.
DDR SDRAM memory is the latest in high-performance memory module technological advances. It offers twice the data bandwidth of previous generation PC100 or PC133 SDRAM, and is now mandatory for high-performance servers and workstations, which need optimal CPU-memory performance. As the name suggests Double Data Rate (DDR) SDRAM doubles the read/write speed of previous generation SDRAM memory. Unlike previous generation SDRAM that used only one edge of each clock pulse, DDR SDRAM references both edges of the clock pulse, effectively doubling the rate of data retrieval out of the memory. Unlike 168-pin SDRAM, DDR SDRAM utilizes a 184-pin plug. Although the basic motherboard technology does not need to be changed, DDR SDRAM is not backward compatible on motherboards designed for previous generation SDRAM.
What is DDR2 Memory?
DDR2 is the next step to higher performance DDR technology enabling faster clock speeds to operate at the higher Front-Side-Bus (FSB) speeds of the newer processor CPU's.
DDR2 can boost designs with greater clock frequency and available bandwidth without increasing power consumption.
The evolutionary changes enable DDR2 to operate between 400 MHz and 533 MHz, with the potential of extending to 667 MHz and 800 MHz.
What DDR RAM is currently available?
New DDR SDRAM DIMMs have 184-pins and run at 2.5 volts. while Previous generation SDRAM DIMMs have 168-pins and run at 3.3 volts.
There are currently, PC2100 (DDR266), PC2700 (DDR333), PC3200 (DDR400), PC4200 (DDR533) These DIMMs are 184 Pin in size and are not interchangeable with previous generation 168 Pin PC 100, PC-133 SDRAM modules.
You still may see the PC1600 (DDR200) , but this is now superceded by the faster models of DDR RAM.
You cannot replace previous generation non-DDR SDRAM with the current new DDR SDRAM RAM due to the physical difference (168-pin with standard DIMMs and 184-pin with DDR RAM DIMM's) and power requirements. There are also two notches on each end of the RAM stick whereas there is only one per end on SDRAM.
In the case of DDR2 RAM, there are currently PC2-4200 (DDR533) and PC2-3200 (DDR400), These DIMMS are 240 Pin in size and are defintely not interchangeable with DDR SDRAM or previous generation SDRAM.
DDR and Bus Speed.
PC2100 refers to the bandwidth of the memory. A PC2100 module has the bandwidth of 2.1GB/sec
therefore it is referred to as PC2100. Also known as DDR266.
DDR266 refers to the effective front-side bus speed of your system. While your DDR system or motherboard may operate at 133MHz front-side bus, its effective front-side bus speed is 266MHz because DDR effectively doubles the amount of data transferred per cycle that a non-DDR system would.
The same holds true for PC2700 (DDR333) which has a bandwidth of 2.7GB/sec and is designed for use in systems and motherboards which require a 166MHz front-side bus, with an effective front-side bus speed of 333MHz.
PC3200 DDR (DDR400) has a bandwidth of 3.2GB/sec and is designed for use in systems and motherboards which require a 200MHz front-side bus with an effective front-side bus speed of 400MHz.
Though DDR memory was designed to be backward compatible (meaning you can use PC3200 DDR in a computer designed to use PC2100 DDR ), we recommend that you purchase the the right memory recommended for your computer. Using PC3200 DDR SDRAM in a motherboard with a 133 MHz bus will result in no increase in speed over using PC2700 DDR.
Traditional SDRAM (Synchronous DRAM)
Almost all systems prior to 2005 used to ship with 3.3 volt, 168-pin SDRAM DIMMs. SDRAM is not an extension of older EDO DRAM but a new type of DRAM altogether. SDRAM started out running at 66 MHz, while older fast page mode DRAM and EDO max'd out at 50 MHz. SDRAM is able to scale to 133 MHz (PC133) officially, and unofficially up to 180MHz or higher. This SDRAM , around mid-to-late 2005, was inhibiting the speed at which the faster Processors were able to clock data in and out of memory. This previous generation SDRAM was becomeing the bottleneck in attaining faster system speeds.As processors got faster, new generations of memory such as DDR and RDRAM were required to get proper performance. DDRAM (Double Data Ram) evolved from the need to search out an alternative to this older style SDRAM to free up this pressing bandwidth limitation.
DDR (Double Data Rate SDRAM)
DDR basically doubles the rate of data transfer of standard SDRAM by transferring data on the up and down tick of a clock cycle. DDR memory operating at 333MHz actually operates at 166MHz * 2 (aka PC333 / PC2700) or 133MHz*2 (PC266 / PC2100). DDR is a 2.5 volt technology that uses 184 pins in its DIMMs. It is incompatible with SDRAM physically, but uses a similar parallel bus, making it easier to implement than RDRAM, which is a different technology.
DDR2
In late 2005 -2006 DDR2 became popular and improved the speed of clocking once again increasing memory speed for the even higher cpu's.
Older RAM types that are now almost obsolete
Fast Page Mode DRAM
FPM DRAM (Fast Page Mode DRAM) is plain old DRAM as we once knew it. The problem with standard FPM DRAM was that it maxes out at about 50 MHz. ( Processors these days are in excess of 533Mhz.)
EDO DRAM
EDO DRAM gave people up to 5% system performance increase over DRAM. EDO DRAM is like FPM DRAM with some cache built into the chip. Like FPM DRAM, EDO DRAM maxes out at about 50 MHz. Early on, some system makers claimed that if you used EDO DRAM you didn't need L2 cache in your computer to get decent performance. They were wrong. It turns out that EDO DRAM works along with L2 cache to make things even faster, but if you lose the L2 cache, you lose a lot of speed.
But these older types are well and truly gone as the new DDR and DDR2 RAM have blitzed them for speed.
Memory Speed
Traditional SDRAM
The traditional SDRAM initially shipped at a speed of 66MHz. As memory buses got faster, the speed was increased to
100MHz, and then 133MHz. These speed grades are referred to as PC66 (unofficially), PC100 and
PC133 SDRAM respectively.
DDR Ram
The faster DDR comes in PC1600, PC2100, PC2700 and PC3200 DIMMs. They are also often referred to as DDR200, DDR266, DDR333 and DDR400 representing the effective FSB clock speeds that they can attain.
DDR2 Ram
The evolutionary changes enable DDR2 to operate between 400 MHz and 533 MHz, extending to 667 MHz and 800 MHz. These can also be termed as PC2-4200 (DDR533) and PC2-3200 (DDR400), and so on.
What is DDR Memory?
DDR memory, or Double Data Rate memory, is a new high performance type of SDRAM memory that runsat twice the speed of previous generation SDRAM. This DDR SDRAM keeps pace with the faster clock speeds of newer processors being released and so ensuring increased overall system speed. The faster the memory, the quicker instructions can be passed to the processor. Previous generation SDRAM had become the main bottleneck in faster processor systems. DDR memory provides roughly a 15% boost in performance compared to previous generation non-DDR SDRAM.
DDR SDRAM memory is the latest in high-performance memory module technological advances. It offers twice the data bandwidth of previous generation PC100 or PC133 SDRAM, and is now mandatory for high-performance servers and workstations, which need optimal CPU-memory performance. As the name suggests Double Data Rate (DDR) SDRAM doubles the read/write speed of previous generation SDRAM memory. Unlike previous generation SDRAM that used only one edge of each clock pulse, DDR SDRAM references both edges of the clock pulse, effectively doubling the rate of data retrieval out of the memory. Unlike 168-pin SDRAM, DDR SDRAM utilizes a 184-pin plug. Although the basic motherboard technology does not need to be changed, DDR SDRAM is not backward compatible on motherboards designed for previous generation SDRAM.
What is DDR2 Memory?
DDR2 is the next step to higher performance DDR technology enabling faster clock speeds to operate at the higher Front-Side-Bus (FSB) speeds of the newer processor CPU's.
DDR2 can boost designs with greater clock frequency and available bandwidth without increasing power consumption.
The evolutionary changes enable DDR2 to operate between 400 MHz and 533 MHz, with the potential of extending to 667 MHz and 800 MHz.
What DDR RAM is currently available?
New DDR SDRAM DIMMs have 184-pins and run at 2.5 volts. while Previous generation SDRAM DIMMs have 168-pins and run at 3.3 volts.
There are currently, PC2100 (DDR266), PC2700 (DDR333), PC3200 (DDR400), PC4200 (DDR533) These DIMMs are 184 Pin in size and are not interchangeable with previous generation 168 Pin PC 100, PC-133 SDRAM modules.
You still may see the PC1600 (DDR200) , but this is now superceded by the faster models of DDR RAM.
You cannot replace previous generation non-DDR SDRAM with the current new DDR SDRAM RAM due to the physical difference (168-pin with standard DIMMs and 184-pin with DDR RAM DIMM's) and power requirements. There are also two notches on each end of the RAM stick whereas there is only one per end on SDRAM.
In the case of DDR2 RAM, there are currently PC2-4200 (DDR533) and PC2-3200 (DDR400), These DIMMS are 240 Pin in size and are defintely not interchangeable with DDR SDRAM or previous generation SDRAM.
DDR and Bus Speed.
PC2100 refers to the bandwidth of the memory. A PC2100 module has the bandwidth of 2.1GB/sec
therefore it is referred to as PC2100. Also known as DDR266.
DDR266 refers to the effective front-side bus speed of your system. While your DDR system or motherboard may operate at 133MHz front-side bus, its effective front-side bus speed is 266MHz because DDR effectively doubles the amount of data transferred per cycle that a non-DDR system would.
The same holds true for PC2700 (DDR333) which has a bandwidth of 2.7GB/sec and is designed for use in systems and motherboards which require a 166MHz front-side bus, with an effective front-side bus speed of 333MHz.
PC3200 DDR (DDR400) has a bandwidth of 3.2GB/sec and is designed for use in systems and motherboards which require a 200MHz front-side bus with an effective front-side bus speed of 400MHz.
Though DDR memory was designed to be backward compatible (meaning you can use PC3200 DDR in a computer designed to use PC2100 DDR ), we recommend that you purchase the the right memory recommended for your computer. Using PC3200 DDR SDRAM in a motherboard with a 133 MHz bus will result in no increase in speed over using PC2700 DDR.
