Chapter | 2 FPGA Architectures 31 One advantage of this implementation is that the main FPGA fabric is identical for devices with and without the embedded microprocessor core, which can help make things easier for the design tools used by the engi- neers. The other advantage is that the FPGA vendor can bundle a whole load of additional functions in the strip to complement the microprocessor core, such as memory, special peripherals, and so forth. 2. An alternative is to embed one or more microprocessor cores directly into the main FPGA fabric. One-, two-, and even four-core implementations are currently available (Figure 2-14 ). In this case, the design tools have to be able to take account of the presence of these blocks in the fabric; any memory used by the core is formed from embedded RAM blocks, and any peripheral functions are formed from groups of general-purpose pro- grammable logic blocks. Proponents of this scheme will argue that there are inherent speed advantages to be gained from having the microprocessor core in intimate proximity to the main FPGA fabric. Soft Microprocessor Cores As opposed to embedding a microprocessor physically into the fabric of the chip, it is possible to configure a group of programmable logic blocks to act