code (or is carefully designed to cope with the change), since the effective clock rate is common to all cogs. The effective clock rate ranges from 32 kHz up to 80 MHz (with the exact values available for dynamic control dependent on the configuration used, as described above). When running at 80 MHz, the proprietary interpreted Spin programming language executes approximately 80,000 instruction-tokens per second on each core, giving 8 times 80,000 for 640,000 high-level instructions per second. Most machine-language instructions take 4 clock-cycles to execute, resulting in 20 million instructions per second (MIPS) per cog, or 160 MIPS total for an 8-cog Propeller. Power use can be reduced by lowering the clock rate to what is needed, by turning off unneeded cogs (which then use little power), and by reconfiguring I/O pins which are unneeded, or can be safely placed in a high-impedance state (tristated), as inputs. Pins can be reconfigured dynamically, but again, the change applies to all cogs, so synchronizing is important for certain designs. Some protection is available for situations where one core attempts to use a pin as an output while another attempts to use it as an input; this is explained in Parallax's technical reference manual. On-board peripherals Each cog has access to some dedicated counter-timer hardware, and a special timing signal generator intended to simplify the design of video output stages, such as composite PAL or NTSC displays (including modulation for broadcast) and Video Graphics Array (VGA) monitors. Parallax thus makes sample code available which can generate video signals (text and somewhat low-resolution graphics) using a minimum parts count consisting of the Propeller, a crystal oscillator, and a few resistors to form a crude digital-to-analog converter (DAC). The frequency of the oscillator is important, as the correction ability of the video timing hardware is limited to the clock rate. It is possible to use multiple cogs in parallel to generate a single video signal. More generally, the timing hardware can be used to implement various pulse-width modulation (PWM) timing signals. ROM extensions In addition to the Spin interpreter and a boot loader, the built-in ROM provides some data which may be useful for certain sound, video, or mathematics applications: a bitmap font is provided, suitable for typical character generation applications (but not customizable); a logarithm table (base 2, 2048 entries); an antilog table (base 2, 2048 entries); and a sine table (16-bit, 2049