[realtek] rtl8139 in a 486?

[Donald Becker]

On Sat, 15 Jul 2000, Luca Olivetti wrote:

> Date: Sat, 15 Jul 2000 00:41:23 +0200
> I have a noname board with a realtek 8139, and it doesn't work reliably in my 
> old 486 (and by browsing the mail archive it seems I'm not the only one with 
...
> I'm using the rtl8139.c version 1.10 in a 2.2.5 kernel (redhat 6.0).
> The chipset is an UMC 8881/8886 (an 486AVIP motherboard, v3.4b/f).
...
> this problem). The problem is that after the first megabyte (more or less) the 
> reception of data is *very* slow.

Does the card work fine in the beginning?
If so, the card could be set back to the fast state.

> Donald Becker suggested in a message (3 
> December 1999) that it is a problem with some buggy 486 chipsets, and a 
> possible solution would be to set RX_DMA_BURST to 1. I tried that but it 
> doesn't work :-(
> Then I found in deja that it can't work, since the pci bus in a 486 is 
> revision 1.0, while these adapter are pci 2.1.

The easy answer is "it won't work".

The true answer is that it's usually possible to get v2.1 products working,
but they usually require setting limits (such as burst limits) that wouldn't
be needed on a PCI v2.0 or later system.  And the changed settings are
likely specific to the chipset used.  In short, it's a driver writer's
nightmare.


Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Beowulf Clusters / Linux Installations
Annapolis MD 21403