PR31100 is is a single-chip, low-cost, integrated embedded processor. PR31100 consists of a 40MHz R3000 3.3V static CMOS CPU with 4 K Instruction / 1 K Data cache memory, w/o MMU, multiple DMA channels and a high-performance and flexible Bus Interface Unit (BIU) and external I/O modules.
PR31500, Poseidon v1.0
PR31500 is a 40MHz R3000 3.3V static CMOS CPU with R3000A TLB and 4K Instrution / 1K Data cache. PR31500 also contains multi-channel DMA controller, ROM, Flash, RAM, DRAM, SDRAM, SRAM, and PCMCIA controller and Dual-UART, SPI and High-speed serial interface controllers.
PR31700, Poseidon v1.5
The PR31700 is a 75MHz R3000 (PR3901 Processor Core) with MMU, 4K Instruction / 1K Data cache. PR31700 also contains multi-channel DMA controller, ROM, Flash, RAM, DRAM, SDRAM, SRAM, and PCMCIA controller. It is also identical to the Toshiba 3912 processor from the TX39XX family. It is pretty clear that Philips licensed or bought this core directly from Toshiba.