Weak current College】 【server memory terminology resolution (reprint).

<br> Server memory is the memory (RAM), and ordinary PC (personal computer) machine memory in appearance and structure does not have any obvious differences of substance, mainly in memory on the introduction of new unique technologies, such as ECC ChipKill, .hot-swappable, technology, etc., with very high stability and error-correcting performance. <br> 1) ECC <br> In a normal memory, often use a technique that Parity check codes with bits (Paritycheckcodes) is widely used in .multi-monitor code (errordetectioncodes), they increase a check bits to each information of characters (or bytes) and can detect a character in all odd (occasionally) and bit error, but there is a drawback, Parity when computer found there is an .error for a Byte, and you cannot determine which bits in error, that error cannot be corrected. Based on the above, generated a new memory error correction technology, ECC, ECC itself is not a memory model that is not a memory dedicated technology, .it is a widely used in various areas of computer instructions, is a kind of instruction error correction technology. ECC full name in English is "ErrorCheckingandCorrecting", the corresponding name is called "error checking and correction", from the name we can see that .its main function is to "find and correct the error," it is better than parity calibration technology more advanced aspects of the main is that it not only can find the error, and correct these errors, the error correction after computer to properly perform the .following tasks to ensure server uptime. Say it is not a memory model, it is because it is not a new affected memory structure and storage speed of technology, it can be applied to different memory types, like the former to "odd correction" memory ., it is not a memory, the start of the application of this technology is EDO memory, SD and application, and ECC memory mainly from SD memory began to be widely applied, and the new DDR, RDRAM also have a corresponding application, the current .mainstream ECC memory is actually a kind of SD memory. <br> (2) Chipkill <br> IBM Chipkill technology is designed to address the current server memory ECC technology developed by inadequate, is a new ECC memory protection standards. We know that the .ECC memory can also detect and correct single-bit errors, but if the simultaneous detection of two more bits of data has errors, the General could do nothing about it. The reason why ECC technology currently in wide use in server memory, it is because .in the past other new memory technology is not yet mature, in addition to the current server in the system speed is still very high, at this frequency generally occur at multiple bit errors phenomenon rarely occurs, because this allows ECC technology is fully recognized and applied ., making the ECC memory technology into almost all the memory on the server. <br> But with the Intel processor-based architecture of the server's CPU performance in a multiple of the geometry class, and the hard drive's performance during the same period only improves .a few times, so in order to obtain adequate performance, the server requires a large amount of memory to temporarily save the CPU needs to read data, such a large amount of data access results in a single memory chip, on every visit is usually to .provide 4 (32-bit) or 8 (64-bit) bit more data to read so much data at once, the possibility of many data errors will greatly improve and ECC cannot correct double bit error above, this is likely to cause all the .bits of data loss, the system will soon collapse. IBM Chipkill technology is the use of the memory of the substructure method to address this challenge. Memory subsystem design principle is that a single chip, no matter how much data width is only for a given .ECC identification number, its impact up to a bit. For example to illustrate is that if you use a 4-bit wide DRAM, 4 bits each bit parity will be composed of different identification code, the ECC ECC identification number is used to separate a .bit to save the data, that is saved in a different memory address space. Therefore, even if the entire memory chips down each ECC identification number will also be up to a bit of bad data, but this situation can be fixed by ECC logic, .thus ensuring fault tolerance of the memory subsystem to ensure that the server in the event of a failure, there is a strong resiliency. This memory technology memory can also check and fix data bit 4 errors, server reliability and stability have been more fully protected. .<br> (3) Register <br> Register is a register or registers, in-memory directory on the understanding that we can put it into the contents of the book, with it, when memory read and write instructions received, will first search .this directory, and then read and write operations, which will greatly improve server memory efficiency. With the memory must Register with Buffer (buffer), and currently can see Register memory also have ECC function, it is mainly used in the high-end server .and graphics workstation. <br> <br> <br> <br>.