What is the typical parallel port speed?

OK, I finally got the par. port working (thanks to nifty little site, **broken link removed**, clear and simple, wish more sites would be like that lol)

I'd like to make a simple function generator (using Dev-Cpp), ie. be able to output a sinewave of an arbitrary freq. onto the par port (which then drives a DAC)...

my question is: what speed does a typical par. port run at - does it depend on the computer's uProc speed?

If have a C++ loop for example, outputting sinewave samples onto the port, does running other programs 'steal' execution cycles from the uProc thereby slowing down the par. port output?

Also, if there are any recommended sites / tutorial on how to implement low / high pass filters / arbitrary transfer functions that would be much appreciated!

many thanks,
gvanto

speed of pc parallel port

Assuming you have direct access to the I/O ports without having to jump through operating system hoops, an IN or OUT instruction to a PC parallel port takes roughly 1 to 2 microseconds, depending on your specific I/O port controller chip. The time doesn't depend much on CPU speed. The CPU comes to a screeching halt during that I/O instruction. It's nice to use DMA if you can figure it out.

Beats me why the I/O is so slow - perhaps to maintain timing compatibility with the old ISA bus.

You can measure your I/O instruction execution time by using the Pentium's RDTSC opcode (it reads the CPU's clock cycle counter).