XSL (eXtended Sparse Linearization) is a recent algebraic attack aimed at the Advanced Encryption Standard. In order to shed some light into the behavior of the algorithm, which is largely unknown, we have studied XSL on equation systems with variables interpreted either as bits or bytes. The algorithm solves byte-systems much faster than it does bit-systems, which promts us to suggest that if a more compact representation of equation systems can be found, such as one where the variables are 8-byte blocks, or even a more generalized form of 8n-byte blocks, it may be possible to increase the speed of XSL dramatically
