EnSilica's eSi-3250 32-bit CPU core is a high-performance processor ideal for integration into ASIC and/or FPGA designs with off-chip memories. The eSi-3250 is suited to a wide range of applications including running complex operating systems such Linux and uClinux.

The processor features separate instruction and data caches that can be configured in size (from 1-64kB) and associativity (direct mapped, 2 or 4-way associative) to increase performance when accessing off-chip memory. The optional paged memory management unit (MMU) enables the implementation of virtual memory and the ability to run operating systems such as Linux.
The 5-stage pipeline allows extremely high clock frequencies to be achieved. While most instructions effectively execute in a single clock cycle, the deep pipeline allows the C and C++ compiler to schedule independent instructions such that instructions that can take multiple cycles to execute, appear to only take 1 clock cycle. Static branch prediction is employed to minimize the cost of branch instructions.

The eSi-3250's instruction set includes arithmetic and logical instructions (including barrel-shift, multiply and divide), comparisons, load and stores, branches and calls as well as system level instructions to control interrupts and enter lower power states. There are also a number of optional instructions and addressing modes that can be selected, should a specific application require them. For example, an set of IEEE-754 compliant single-precision floating point instructions are available. For those applications that require extreme performance or ultra low power operation, user defined instructions can be implemented.

Instructions are encoded in either 16 or 32-bits, depending upon the size of the operands and the type of instruction. All of the commonly used instructions can be encoded in 16-bits. This ensures that high code density is achieved, which helps to increase performance by increasing the number of instructions that can be stored in the instruction cache. The processor supports both user and supervisor operating modes, with privileged instructions and memory areas, to allow an O/S kernel to be fully protected from user applications.

The toolchain for the eSi-3250 is based upon the industry standard GNU toolchain, which includes an optimising C and C++ compiler, assembler, linker, debugger, simulator and binary utilities. All these tools can be driven by the customizable Eclipse IDE (Integrated Development Environment). The debugger can connect to the target CPU either via JTAG or a serial interface. Complete C and C++ libraries are supplied. A port of the Micrium uC/OS-II RTOS is also available. The toolchain is available for both Windows and Linux hosts and is available to use at no cost.