Re: 3Com ethernet card not being detected

Paul Gortmaker (gpg109@rsphy6.anu.edu.au)
Thu, 13 Jun 1996 05:36:10 +1000 (EST)


> > If your systems have PCI and you think you may go to 100Base-TX in the
> > future, you may want to consider the 3Com 3c595 instead. Only about
> > $30 more.
>
> Or SMC etherpower and other tulip based cards. The benchmarks (ttcp) say the
> etherpower is faster and has less CPU load
>
> Alan
>

No surprise about 3c59x CPU load. You only get PIO mode, unless you
explicitly enable vp->bus_master, which will still only get you
bus-master xfer on Tx packets. (Typical "desktop" usage is usually
heavily biased towards Rx'ing) This little snippet from the driver
says it all about the PIO vs. bus-mastering 3c59x support.

----------
III. Driver operation

The 3c59x series use an interface that's very similar to the previous 3c5x9
series. The primary interface is two programmed-I/O FIFOs, with an
alternate single-contiguous-region bus-master transfer (see next).

One extension that is advertised in a very large font is that the adapters
are capable of being bus masters. Unfortunately this capability is only for
a single contiguous region making it less useful than the list of transfer
regions available with the DEC Tulip or AMD PCnet. Given the significant
performance impact of taking an extra interrupt for each transfer, using
DMA transfers is a win only with large blocks.
----------

Paul.