A graphics system is provided to implement compression of depth or z-data. The graphic system includes a buffer, a status table, and a read/write unit. The buffer stores depth data for multiple blocks of pixels in associated buffer entries. The status table stores status values for the entries of the buffer. The status value for a given entry indicates an access mode for the corresponding depth data according to whether the data is compressed, uncompressed or in a reference state. The read/write unit implements data accesses for a given entry responsive to the status value associated with the entry.