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Classifying Memory
There are multiple classifications for RAM: memory module type, chip type, speed, and parity. Memory modules vary by type, which is defined by the motherboard and the motherboard’s form factor. Memory modules are defined by the number of pins they have on the modules, like 240-pin DIMM (dual in-line memory module), 184-pin DIMM, etc.
RAM is also classified based upon memory chip type. In the past, systems used different types of chips based on their manufacturer, but current systems use mostly the same type, usually DDR (dual data rate), DDR2, or DDR3. Although the DDR is the most common type, some unique systems may use RDRAM (Rambus dynamic random access memory).
Another RAM classification is based on speed. Older memory was classified in nanoseconds (for example, 60 nanoseconds). Over time, all memory became nearly the same speed, as measured in nanoseconds, so they changed this to bus speed (for example, PC-133 memory operates at a bus speed of 133 MHz). Most contemporary memory is now measured in throughput (PC2-6400, which operates at 800 MHz but has 6.4 GBps of bandwidth).
Finally, memory can be purchased with and classified by parity, non-parity, or ECC. Parity memory checks for errors as data is read/written to the chip. While parity memory can detect an error, it cannot correct it. Non-parity memory, one of the most common types found in desktop computers, has no error checking ability. Error correcting code (ECC) is an advanced version of parity that can find an error and correct that error as it is read/written from the chip. Due to these additional functions, ECC tends to be slower than equivalent non-parity RAM.
RAM有多種分類：內存模塊類型，芯片類型，速度和奇偶校驗。內存模塊因類型而異，具體取決於母板和母板的外形尺寸。內存模塊由其上的針腳數量定義，例如240針DIMM（雙列直插式內存模塊），184針DIMM等。 RAM也根據存儲芯片類型進行分類。過去，系統根據製造商使用不同類型的芯片，但是當前的系統大多使用相同類型的芯片，通常是DDR（雙數據速率），DDR2或DDR3。儘管DDR是最常見的類型，但某些獨特的系統可能會使用RDRAM（Rambus動態隨機存取存儲器）。 另一個RAM分類基於速度。較舊的內存以納秒（例如60納秒）分類。隨著時間的流逝，所有內存的速度幾乎相同，以納秒為單位，因此他們將其更改為總線速度（例如，PC-133內存以133 MHz的總線速度運行）。現在，大多數當代內存都是按吞吐量衡量的（PC2-6400，工作於800 MHz，但具有6.4 GBps的帶寬）。 最後，可以使用奇偶校驗，非奇偶校驗或ECC購買內存並按其分類。奇偶校驗存儲器在將數據讀/寫到芯片時檢查錯誤。儘管奇偶校驗內存可以檢測到錯誤，但無法糾正錯誤。非奇偶校驗內存是台式計算機中最常見的類型之一，沒有錯誤檢查功能。糾錯碼（ECC）是奇偶校驗的高級版本，可以發現錯誤並在從芯片讀取/寫入該錯誤時糾正該錯誤。由於這些附加功能，ECC往往比等效的非奇偶校驗RAM慢。
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