> Richard Gooch wrote:
>
> > On my tests I noticed quite a spread of times. When I send short
> > packets, then yes, the times are around a few hundred
> > microseconds. However, for longer packets, I was getting up to 2
> > milliseconds. And my measurements were consistent with the results
> > other were getting with pSOS. I first instrumented almost the whole
> > interrupt handler, then later just instrumented the block transfer
> > routine and got the same results.
>
> Rule-of-thumb calculation: ISA bus cycle costs 1 us (one microsecond).
> 1500 bytes -> 750 transfers (Ne2000 is 16bit card) -> 750 us.
ISA PIOW (16-bit) is 300ns per word. There is overhead setting it up, etc.
ISA PIOW (8-bit) is a horrific 750ns per word. We do this all the time
so the numbers are quite well known here.
750 * 300ns = 225us
Cheers,
Dick Johnson
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