Binary strings of data is basically how a computer uses memory. Data integrity is a method of arranging data that adds one bit of extra data the parity bit, along with each 8-bit bus cycle. This method is commonly know as parity.
There is a three step process to validate bus transaction, which refers to bus cycle which is the transaction between the CPU and the memory. Parity memory is supported by some older motherboards while non-parity memory is supported by some newer motherboards.
It's really simple if there is a odd number of chips or integrated circuits (IC) on the parity memory module which most likely is a single inline memory module (SIMM) it is considered parity if there is an even number of chips it is considered nonparity.
The integrity of the data stored in the parity memory which is validated by counting the number of bits set to 1, in a determination of the number of chips either being even or odd. With that determination the parity memory can now set the number of 1-bits to either even or odd, resulting in even parity memory or odd parity memory.
The number of 1s is counted when the data is read. The CPU will stop processing data if the number of 1s is odd but the parity is even, resulting in a parity error. Most new mother boards on the market today use nonparity memory.
As you may already know memory modules are sold by there size and speed, size meaning in megabytes and speed meaning megahertz. There is a real difference in the quality of memory that can be purchased.
Low cost memory can create a variety of errors and make an operating system very unstable. For high performance computers use the fastest memory the motherboard will support, but do not exceed the mother boards maximum speed supported.
General not a good idea to mix memory speeds though it is possible. All mother boards have either tin or gold connectors inside the memory banks, it is recommend to match tin with tin and gold with gold meaning that if you have a motherboard that has gold connectors in the memory banks, only install memory with gold leads.
Error Checking and Correction or ECC is a chipset that is supported by some synchronous dynamic random access memory modules or SDRAM memory. Normally on a Duel inline memory module or (DIMM) there are 8 chips but if it is an ECC memory module it will have a ninth chip the ECC chip.
A ECC memory module can be identified as being a 72-bit DIMM as opposed to a 64-bit DIMM. The error correction process lies in the extra 7 bits that is used to validate the reliability of ever 64 bits stored on a memory module and when possible correct any errors found.
Ok one last time in english the best definition so far is that they way ECC memory works is that there is a chip set on a motherboard that checks the integrity of the data stored in DIMMs and can correct single bit errors in a byte. Got it? Good cause I'm giving myself a headache.
Major types of Memory
If you have been over to our system memory page you would have read some good overall information on memory, however there is not enough information on that page about all the different types of memory and the way memory functions, so being the great guy that I am I've and decided to talk more about the different types of memory.
Believe it or not it's been more than 20 years since the first IBM computer was released to the market as a PC (personal computer.) Since then technology has allowed the computer to developed and grow and along with that growth every step of the way computer memory has evolved and become more reliable and efficient, memory has grown in leaps and bounds as far as capacity and speed are concerned and really I don't see and end to the growth and development of system memory anytime soon.
When memory was in in infancy stage it was very expensive and personal computers did not have much memory in them because of the cost to the consumer, thus leaving the costly memory to large business who needed to have higher amounts of memory in servers and workstations that demand more memory to able to work properly. However as the demand for higher amounts of memory for applications and games began to grow, memory became more and affordable and more accessible for people with personal computers.
This with the demand for memory form the business market and now the consumer market three types of memory have been the standard of choice. As mentioned in the system memory page the oldest of the three types of memory is the SDRAM or Synchronous Data Ram. Next is the RDRAM Rambus Dynamic Ram and finally DDR double data Ram.
SDRAM- Synchronous Dynamic Ram
In the mid 1990's SDRAM was introduced to the market and and it was a significant step in improvement over the older types of RAM it was developed from. SDRAM has three speeds 66MHZ, 100MHZ, and 133MHZ and thus could match the speed of the system bus when required of it. This allowed the CPU to keep humming along instead of being in a "wait state" therefore not having to wait for the memory to catch up with it. The advancement for SDRAM allowed one bit of memory to be accessed while the next bit of memory was being primed or prepared to be accessed. By having the next bit of memory prepared this allowed for a burst of memory and did not slow down the flow of data from the CPU which meant fewer stalls or shutdown in the entire process. The end result in all of this happiness is a about 800Mbps of data transfer rate through a 100MHZ system bus and about 1Gbps on a 133 MHZ bus.
SDRAM is made of a 168-pin dual inline memory module or DIMM, with four different memory sizes 32,64,128 and 256 Mega Bytes, along with three different speeds as mentioned above PC66, PC100 and PC133 Mega Hertz.
RDRAM-Rambus Dynamic RAM
Right on the heels of SDRAM came RDRAM in the late 1990's with lots of speed and expectation along with it brought some problems. RDRAM availability was poor which made it a very expensive memory to buy and stock for vendors, as a result this expense was passed on to the consumer. The odd thing about RDRAM is that it was first made available to the consumer market because of it's speed and reliability almost the opposite of SDRAM when it was mainly just available for this business side of the market. The price of a personal computer that had this newer faster more reliable memory grew tremendously, making consumers think twice about purchasing a computer that had RDRAM installed, however the market was there and people that could afford higher end computer bought those computers with the new fangled RDRAM.
So what they heck is so special about RDRAM? Well for started there are actually two types of Rambus memory, and they are used in other types of devices instead of just computers. Do you have a Sony PlayStation 2? The PlayStaion 2 uses and has installed in it two Rambus modules, as opposed to the computer RAM bus which is referred to as Direct RAMBUS/RDRAM.
DDR-Double Data Rate Synchronous Dynamic Ram
Also know as DDR RAM, Double Data Ram, and DDR SDRAM all these names refer to the same high speed type of memory. Advance Micro Devices (AMD) supported this type of memory heavily and so did mother board manufactures. DDR Ram was developed to compete with the very expensive RDRAM the Intel Corporation was pushing for it's Pentium IV line of personal computers workstations as well as servers, in which RAMBUS was also installed in Intel Pentium III based Xeon servers.
The major issue with RAMBUS type of memory was the cost, and many computer and motherboard manufactures preferred the DDR type of memory because it was so much more affordable to them and consumers. In addition RAMBUS lacked the speed to provide data for faster CPU's that were coming out on the market.
AMD saw the opportunity and began building more systems base on DDR memory, consumers loved the idea of having a faster more reliable system with out having to pay the heavy cost RAMBUS memory. This woke up Intel and Intel began to use less and less of RAMBUS type memory in all of there systems, and announced that it would to begin using DDR type memory.
What makes DDR Ram so efficient is that it tries to double the speed of the older type of SDRAM. Ranging in data-transfer speeds of 1.6GPS and 2.1GPS and compared to SDRAM with it's speeds of 800MBPS and 1GPS. Physical the two types of memory do not look all that different unless there are examined closely. DDR has one notch that lines up with the memory bank and SDRAM has two notches, in addition SDRAM has 168-pins while DDR has 184-pins.
