In this paper we present SADDLE, a modular framework for automated design of cluster supercomputers and data centres. In contrast with commonly used approaches that operate on logic gate level (Verilog, VHDL) or board level (such as EDA tools), SADDLE works at a much higher level of abstraction: its building blocks are ready-made servers, network switches, power supply systems and so on. Modular approach provides the potential to include low-level tools as elements of SADDLE's design workflow, moving towards the goal of electronic system level (ESL) design automation. Designs produced by SADDLE include project documentation items such as bills of materials and wiring diagrams, providing a formal specification of a computer system and streamlining assembly operations.