This paper introduces a new unobtrusive and cost-effective method for the capture and compression of program execution traces in real-time, which is based on a double move-to-front transformation. We explore its effectiveness and describe a costeffective hardware implementation. The proposed trace compressor requires only 0.12 bits per instruction of trace port bandwidth, at the cost of 25K gates. Categories and Subject Descriptors B 7.2 [Integrated Circuits]: Design Aids-Verification. D.2.5: [Testing and Debugging]: Debugging aids, Tracing. General Terms Design, Verification. Keywords Debugging, Program Trace, Compression.