[U-Boot-Users] MPC8xx-board: just 10MBit transfer rate

Jerry Van Baren gerald.vanbaren at smiths-aerospace.com
Tue Mar 14 16:58:28 CET 2006

Josef Angermeier wrote:
> Dear u-boot users,
> i got u-boot 1.1.3 and linux 2.4.25 running on my custom MPC875-board.
> But the ethernet-connection (FEC-Controller) seems to be abit slow. The
> MII-transceiver chip autonegotiates a speed of 100MBit but when
> downloading files via tftp/ftp in u-boot or linux the transfer seems to
> happen in 10MBit mode.
> Could this be caused by the low system clock (40MHz) ? What else ?
> Best regards,
> Josef

Crank up ethereal and see what packets are being transmitted, received, 
and the time between packets.  I suspect you will see either gross 
delays or retransmissions (and quite possibly both), indicating packet 
handling problems of some form or another. (Unreasonable to speculate 
what, without seeing the ethereal dump.  Once you see the packet 
pattern, the problem usually is fairly obvious.)

If not, you need to recalibrate your expectations. :-)  TFTP is a 
transmit-acknowledgment protocol with no pipelining, so packet n+1 
doesn't get transmitted until packet n is acknowledged.  If the <ack> is 
slow, your transfer rate will be slow also.


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