Future lithography systems must produce more dense microchips with smaller feature sizes while maintaining throughput comparable to today’s optical lithography systems. This places stringent data-handling requirements of up to on the design of any maskless lithography system. In past work, we have developed data-path architectures for such throughput and shown that lossless compression algorithms play a key role in such systems. We currently investigate the effectiveness of the Block C4 lossless layout compression algorithm in increasing throughput of direct-write maskless lithography systems. In particular, we characterize the compression efficiency of Block C4 on blocks of select layers of two chips: a state-of-the-art microprocessor chip and a low-density parity code chip used commonly in wireless communication applications. Overall, we have found that compression efficiency varies significantly from design to design, from layer to layer, and even within parts of the same layer. We propose a number of ways to cope with the variation of compression ratios within a layer and characterize the way each method affects the overall wafer layer throughput.