I found the manufacturer's web page for that modem:
http://broadband.motorola.com/noflash/sb5100.html

But I ask again - are you using an Ethernet cable or a USB cable to hook the modem up to the Mac ? If you need help in understanding the question or in telling the difference between these two different types of cables, let us know.

(Here's an image that shows what the USB symbol looks like:
http://www.iomega.com/support/manual...ct_usb_com.gif )

Actually, he seems to have problems with both. I suspect the cable modem.

His PC:

Web100 reports the Round trip time = 123.74 msec; the Packet size = 1380 Bytes; and
No packet loss - but packets arrived out-of-order 34.47% of the time
This connection is receiver limited 79.43% of the time.
Increasing the current receive buffer (63.0 KB) will improve performance
This connection is network limited 20.41% of the time.
Contact your local network administrator to report a network problem
Contact your local network admin and report excessive packet reordering

His Mac:

No packet loss - but packets arrived out-of-order 44.97% of the time
This connection is network limited 99.85% of the time.
Contact your local network administrator to report a network problem
Contact your local network admin and report excessive packet reordering




My Mac:

Web100 reports the Round trip time = 163.30 msec; the Packet size = 1368 Bytes; and
No packet loss was observed.
This connection is receiver limited 92.79% of the time.
Increasing the current receive buffer (63.0 KB) will improve performance
This connection is network limited 7.05% of the time.

Did tests too, and both mac and PC come up with something around .2% being out of order, wish is ok... but the numbers coming out for this cable modem are incredibly high... Probably the source of the issue indeed... Maybe its in need of firmware updates ?

i am using ethernet cable to connect the modem between the two
computers. the modem is new and the cable is new plus i have
tried using other cables with the same results.



P....

This is all quite strange, but I would suggest you do as cwtnospam has suggested above - buy a router (which, as he has said, you will be needing anyway in order too be able to connect more than one computer to Internet) and plug the router into the modem and then plug your Mac into the router and redo the bandwidth tests.

Yes, a router may help. Remember, however, that you are having some problems, although not as severe, with the PC's connection, too. That's why I suspect the cable modem. It could also be the drop from the street to your home, or signal leak(s) in the house. If it's any of these, the company to call is your cable provider.

the cable drop from the pole to the house and then to the modem is
all 2 weaks old. the modem is 2 weaks old.

i bought a Linksys router this morning and hard wired both machines
into it.

on the laptop pc i get 3.5-4.0 Mbps
on the mac i get 1.5 - 2.5 Mbps

the packets-out-of-order is about the same on both machines.

i called motorola and they had me bring up a diag page showing the
download "SNR" being 35db and the download power lever at 7db
the upload power lever is 39 dBmV and told me there is nothing
wrong with the modem and that i should call the cable provider.



P....

Do you have any cables coming out of the wall, but not plugged into anything like a tv or cable modem? Have you spliced any of the coaxial cable yourself?
I'm thinking signal leak is affecting the Mac more than it is the PC for some reason.

Edit:
When you call the cable company, be sure to show them that BOTH computers are affected. The PC is merely less affected. This is critical because it demonstrates that the problem is somewhere from the cable modem to their office.

This seems pretty definitive in indicating a problem on the Mac.
But just to be sure, did you unplug the PC when doing the test on the Mac (and vice versa) so that you are sure that the other machine is not using any network bandwidth?
And you swapped the cables and ports you are using between the PC and Mac as well - to eliminate all possible variables?

I disagree. Both systems report packets arrived out of order. Something external is causing that.

I'm wondering if the packets that the Mac is sending are larger than the PCs. If they are, they would be more susceptible to interference and that would explain the slower speed and packets arriving out of order. Anyone know the answer or how to find it?
I know this still leaves the underlying problem, but it may help us understand what's going on. :rolleyes:

Please check your MTU and Firewall settings... :)

A similar disparity between bandwidth as measured on a PC and Mac was reported in this other thread:
http://forums.macosxhints.com/showthread.php?p=178976
There it was found that the problem was due to network settings that had been changed by Broadband Optimizer. Putting the settings back to the system defaults solved the problem.

Make sure your Mac isn't doing anything else on the network - one other throttled IP task can cut your bandwidth in half. Any P2P programs running (eDonkey/Acquisition)? If you're not sure, show us the results of:

sudo netstat -na | grep ESTABLISHED

Also, if you have the Mac OS X firewall on, turn it off.