Thursday, August 1, 2013



What do you get with a COSMAC ELF in FPGA? You get an Elf that's 100 times faster than the original.

Project by Eric Smith. "The original COSMAC Elf ran at 1 to 2 MHz.  Every machine cycle required eight oscillator cycles, and each instruction required two or three machine cycles, so each instruction took 8 to 12 microseconds at 2 MHz, or 16 to 24 microseconds at 1 MHz.

The FPGA-Elf runs at 25 MHz when using a Spartan-3E FPGA in the slow speed grade, but it also needs only one oscillator cycle per machine cycle.  That means that each instruction takes 80 to 120 nanoseconds.  That’s 100 times the speed of a 2 MHz COSMAC Elf!"