Sprow ARM7TDMI Co-Processor
BeebEm emulates the Sprow ARM7TDMI Co-Processor. The co-processor features an ARM7TDMI processor running at 64MHz, 512kbyte on-board flash ROM (containing system software and BASIC), and 64Mbyte RAM.
You start the Sprow Co-Pro by selecting ARM7TDMI Co-Processor on the Hardware → Second Processor menu. BeebEm comes with version 0.40 of the system software in the file sprow.rom in the BeebFile folder.
You can find more information about this co-processor on Sprow's website.