Modern platform FPGAs are sufficiently dense to allow the assembly of a complete chip heterogeneous multiprocessor systems on chip (CHMPs) within a single die. Based on CHMP, every research group that sets out to explore how an application can be accelerated on an FPGA platform must firstly integrate processors, buses, memories, and support IP components into a base architecture prior to beginning their application specific analysis. Lacking of computer architecture background, many application developers will spend significant amounts of valuable research time to create and debug the base CHMP system. In this paper, we present Archborn, an open source tool that automates the generation of modifiable CHMP architectures. Archborn can be used by application developers to create a base CHMP system that can be synthesized in seconds. The systems created by Archborn can also be modified by those who wish to create fully customized CHMPs systems.We show the ease and flexibility of Archborn by automatically generating three unique systems: an NUMA architecture that is modified with an Hthreads hw/sw co-designed microkernel for multithreading, and a NUMA architecture to support the OpenCL programming model.We present analysis on resource utilizations and scalability for creating systems with up to 64 processing elements (PEs).