Early compression tag lookup for memory accesses

A method of writing a surface stored in memory that includes compressed data and non-compressed data, comprising:

• producing a write request by a compression aware client to store new data in a tile mapped to the surface;
• reading a compression tag corresponding to a position of the tile from a compression tag cache;
• determining that existing data stored in the tile is represented in a compressed format;
• outputting the write request for arbitration to access the memory in order to store the new data in the tile;
• arbitrating the write request with other read and write requests, including other read and write requests produced by a naive client that is only able to read and write non-compressed surfaces, to produce arbitrated read and write requests;
• and
• reordering the arbitrated read and write requests, based on a size of the write request that is indicated by an updated compression tag for the new data to produce reordered requests that are in a different order than the order in which requests are received from the compression aware client.

A system for accessing a surface stored in memory that includes data represented in a compressed format and data represented in a non-compressed format, comprising:

• a compression aware client configured to produce the data represented in the compressed format or the data represented in the non-compressed format for storage in tiles mapped to the surface and to produce read and write requests to access the surface;
• an arbitration unit configured to arbitrate between the read and write requests produced by the compression aware client and read and write requests produced by a naive client that is only able to read and write non-compressed surfaces to produce arbitrated read and write requests;
• a compression tag storage coupled to the arbitration unit and configured to store a compression tag indicating whether each one of the tiles mapped to the surface stores the data represented in the compressed format or the data represented in the non-compressed format;
• a request unit that is coupled between the arbitration unit and the memory and configured to reorder the arbitrated read and write requests produced by the compression aware client based on the compression tags to produce reordered requests that are in a different order than the order in which the requests are received from the compression aware client;
• a returned data buffer coupled between the arbitration unit and the memory and configured to buffer the data stored in the tiles in an amount of memory that is allocated by the arbitration unit based on the compression tag for each one of the tiles, wherein entries in the returned data buffer are allocated in the order in which read requests are received from the compression aware client;
• and
• a compression tag cache coupled between the compression aware client and the compression tag storage and configured to process compression tag writes received from the arbitration unit and process compression tag reads received from the compression aware client.