On Tue, Apr 09, 2002 at 07:35:23PM +0200, Wojciech Puchar wrote:
> any reason why this card works deadly slow on 486/100 PCI+ISA machine.
> 
> tried ISA clock=PCI/3 to PCI/6 no change
> 
> max transfer 20kB/s through FTP, while telnet sessions goes smooth.
> 
> no packet loss with pings up to 3000, over 3000 100% packet loss.

ok - so the boundary is somewhere near where 3 IP fragments
are required.

My guess is that the card doesn't have enough rx buffer space
(anyone know how much RAM is on the 3c509?) for the third
packet. And the system isn't reading the data out very quickly.
> 
> this card works well on other machine

It is possible that the 'other' system is doing faster IO cycles
when reading data from the card, so manages to keep up (or at
least not get so far behing so quickly).

Some of the old PCI systems cannot do fast ISA bus cycles
- too many bridges in the way!
This includes some 'server' motherboards.
A 486 ISA (only) system probably does better.
I suspect modern systems have more silicon in the bridges.


	David

-- 
David Laight: david@l8s.co.uk