The present invention relates to a method and apparatus for rasterizing images in a computer graphics display system to provide increased read-back performance. In a texel rasterizer of the computer graphics display system, a single bus is used for communicating immediate mode commands and data and variable mode commands and data. Object read commands, which are variable mode commands, are used to read objects from cache and return them to the front end component of the texel rasterizer. Object read commands are issued and completed in approximately 40 states, although the exact amount of time required to perform the transaction cannot be ascertained. Timing signals generated within the texel rasterizer allow the front end component of the texel rasterizer to prefetch objects from cache and to keep track of the number of object commands which have been issued which have not yet been completed. When an object command is issued from the front end component to a tiler component of the texel rasterizer, a signal is output by the front end component to the tiler component which indicates that a valid object read command has been issued to the tiler. When a valid object is returned to the front end component by the interpolator of the texel rasterizer, a signal is output from the interpolator to the front end component indicating that a valid object has been returned.