Re: NE2000 slow interrupts safe?
Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Fri, 17 Apr 1998 22:36:08 +1000
Following up on this again, this time with tests using 2.1.90
(previous tests were with 2.0.33).
Rogier Wolff writes:
> 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.
>
> I'd say 2000 us is quite long, 300 us is a pretty fast.
>
> I guess that you can have ne2000's that are slower than others. Maybe
> 300 us was a PCI card?
The test was done with an ISA card. I've re-run the tests on a Pentium
200 MMX with an ISA NE2000 card (el cheapo). The 8390 interrupt
service routine often takes 4 ms. The ne_block_input() function takes
around 1.1 ms. This is when I'm sending a megabyte of data to the
machine using TCP, so the EtherNet packets should be close to 1500
bytes. The lower times would be due to shorter received packets. This
machine is running 2.1.90.
I've done similar tests on a dual PPro with a PCI NE2000 (also an el
cheapo), and I get similar times for ne_block_input(). However the
whole 8390 interrupt routine has gone down to around 2 ms. This
machine is 2.1.91.
On a P90 system with an ISA SMC-ULTRA I recall getting up to 2 ms per
interrupt. That machine was running 2.0.33.
Regards,
Richard....
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