Patent US 5,201,041

An inpage buffer is used between a cache and slower storage device. When a processor requests data, the cache is checked to see if the data is already in the cache. If not, a request for the data is sent to the slower storage device. The buffer receives the data from the slower storage device and provides the data to the processor that requested the data. The buffer then provides the data to the cache for storage provided that the cache is not working on a separate storage request from the processor. The data will be written into the cache from the buffer when the cache is free from such requests. The buffer is also able to provide data corresponding to subsequent requests provided it contains such data. This may happen if a request for the same data occurs, and the buffer has not yet written the data into the cache. It can also occur if the areas of the cache which can hold data from an area of the slower storage is inoperable for some reason. The buffer acts as a minicache when such a catastrophic error in the cache occurs.