archive: Re: SETI Re: High bandwidth digitizer, FFT's, and analyzer

Re: SETI Re: High bandwidth digitizer, FFT's, and analyzer

MarcusJohn@aol.com
Sat, 3 Oct 1998 13:35:29 EDT

In a message dated 10/3/98 5:46:48 AM Eastern Daylight Time,
david@djwhome.demon.co.uk writes:

> Regarding cycle count, I think MMX includes some array processing and it
> *might* be possible to hand craft MMX assembler to do better. There would
> also be some improvement by unrolling the inner loop. Both ways I think
> you are still in the mid 100s of kHz. The average cycle count of two
> is a finger in the air guess, but the 64 bit multiplies, needed for the
> 100MHz system, are unlikely to be cheap. The specgrm code has twice as
> many multplies as the text book says it should have, although this only
> slightly decreases the instruction count - the cycle count would go do
> rather more

Well, thanks for helping clear that up. Now I have a bandwidth limit for the
FFT processing of a PC. Have your figures taken into account the vast
improvement in speed from changing the real mode math to integer math (ala the
tremendous fractal graphics program Fractint)? I suspect that your
calculations are done using real mode math, instead of integer mode.

Thanks,
John Marcus MD.
KE3SW.