On Mon, 19 Jun 2000, Andrew Morton wrote:
> > > I have a 400MHz Celeron UP here which is running at 100% when sending 10
> > > MBits/sec with an EISA card (cs89x0).
> >
> > Unless the cs89x0 driver is doing something unusual, or you application is
> > CPU hungry, that sounds a little off. We could saturate a 10Mbps Ethernet
> > with a 386.
>
> I was a while ago.. I recall that the driver took half a millisecond to
> write a 1 kbyte packet out over the EISA bus (PIO), and that this was by
> far the dominating factor. Plus I had reduced the ISA clock a bit due
> to bits getting dropped during DMA Rx into memory...
EISA or ISA? (I expect you mean ISA.)
The ISA bus is usually run at 8.00 or 8.33 Mhz, and takes 3 or 4 cycles to
transfer a 16 bit word with bulk data. That gives a maximum rate of
4.0-5.4MB/sec, with the CPU doing nothing but waiting on the ISA bus.
Using ISA slave DMA results in a significantly lower data rate, but the CPU
has a chance to do a little something else while setting up the DMA
controller.
Using ISA master DMA (e.g. the AMD LANCE and PCnet/ISA) is better, but this
does work with many older motherboards or ISA-PCI bridges.
Using 8 bit ISA cards such as the NE1000 is actually less than half the
speed, since each transfer takes an extra cycle.
It's possible you have hardware that uses an extra bus wait state. That
would explain the low transfer rate.
> > > With a PCI NIC (3c905) it will do 100Mbits/sec at 60% CPU.
> >
> > Also high: you should be able to drive at least two, almost three, 100Mbps
> > channels with a P5-100.
>
> Does that include TCP and application overhead?
Yes, that number was with a user-level application reading full-sized data
packets. An application that does other I/O, uses smaller packets, consumes
a lot of CPU time or flushes the cache will, of course, have lower
performance.
Donald Becker [EMAIL PROTECTED]
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Annapolis MD 21403
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