[20091112]a write back cache

 write-back cache 

 

A caching method in which modifications to data in the cache aren't copied to the cache source until absolutely necessary. Write-back caching is available on many microprocessors, including all Intel processors since the 80486. With these microprocessors, data modifications (e.g., write operations) to data stored in the L1 cache aren't copied to main memory until absolutely necessary. In contrast, a write-through cache performs all write operations in parallel -- data is written to main memory and the L1 cache simultaneously. 

Write-back caching yields somewhat better performance than write-through caching because it reduces the number of write operations to main memory. With this performance improvement comes a slight risk that data may be lost if the system crashes. 

A write-back cache is also called a copy-back cache. 

写回缓存

一种缓冲方法，一般情况下缓存中被修改的数据不会被复制到缓冲源。写回缓寸用于许多微处理器，包括自80486所有的英特尔处理器。这些微处理器中，数据修改（例如：写操作），可以被储存在L1缓存中，直到必要时才被写入主存。相比之下，写穿（write-through）缓冲并行地将写操作数据写入L1缓存和主存。

写回缓存在性能上优于写穿缓存，因为减少了对主存的写入次数。这个性能改善同时也增加了一些轻微的风险，比如如果系统崩溃，数据可能会丢失。

写回缓存同时也被称作拷贝回（copy-back ）缓存。