Motorola cable modems slower with some Macs than with PCs (#2): Workarounds; Word from Motorola; more
Motorola cable modems slower with some Macs than with PCs (#2): Workarounds; Word from Motorola; more
We've received overwhelming response regarding an issue affecting some Motorola SurfBoard cable modems that results in lower throughput speeds when the devices are connected to Macs than when the devices are connected to Windows-based PCs.
Dozens of readers have now reported that their Motorola modems deliver significantly lower throughput when connected to Macs than when connected to PCs.
MacFixIt reader Jim provides a typical case example:
"A few years ago, about 5 years ago actually, I asked the local cable company come to the home and test my internet connection on my Mac. My internet connection operated slower than my friend's PC with the same cable company and modem.
"The cable company came and brought a PC notebook along to test the connection from my end. Their PC notebook demonstrated a download speed in excess of 450KB/sec, where my Mac could only obtain a maximum download speed of 250 KB/sec.
"The cable person suggested it was a problem with my Mac, and how it communicated with the cable modem. I found that answer troubling, so I sent an email to you folks at the time, asking if your viewers had any similar problems. The original email and your response were discarded a long time ago.
"I upgraded from the Motorola CyberSURFER Wave Modem to the SURFboard modem, model SB5101, when it became available about three years ago. The issue of the differential speeds between a Mac and a PC was still present, even with the newer faster modem design.
"The cable company came to the home and conducted the same test and we experienced the same results, with the same answer regarding the Mac's inability to communicate with the modem properly. The speed difference in my opinion is quite significant, and totally annoying that this condition exists."
Meanwhile, MacFixIt reader Mike Lovstedt resorted to a cable modem from another manufacturer:
"I too had this problem. I had the latest motorola cable modem from our ISP Comcast. My PC would get the 8 Mbps download speed that Comcast advertised, but my Mac would get 1.4 Mbps as a max. Comcast couldn't find a cure.
"Following the advice of others, I replaced it with a cheaper D-Link cable modem from OfficeDepot (with the TI chipset) and now the mac also gets the faster speeds."
Workaround: Changing TCP settings Some readers have been able to achieve much better throughput by modifying specific TCP parameters using a tool like Sustainable Softworks' IPNetTunerX.
MacFixIt reader Michael Schmitt found success with the following settings:
- kern.ipc.maxsockbuf = 512000
- net.inet.tcp.delayed_ack = 0
- net.inet.tcp.recvspace = 65536
- net.inet.tcp.sendspace = 65536
- net.inet.udp.recvspace = 73728
Michael writes:
"With these settings I get the full 6 Mbps speed from the PowerBook. If I recall correctly, turning off delayed acks is what really helps. I think that Windows has different TCP/IP defaults, accounting for the faster networking speed out of the box."
Recommendation from Motorola: Use an older modem As we reported yesterday, using an older Motorola cable modem can actually result in faster throughput, as the older modems do not use DOCSIS. This has now been confirmed by a Motorola representative who writes:
"I did some more research on it, and the problem seems to be only with DOCSIS capable modems, if you were to use an older modem, it would perform faster, I know that sounds crazy but that's what some Mac users have found out. It's not going to be the hardware itself if it works fine on Windows and Linux operating systems."
Intel-based Macs achieving better throughput? Some users are reporting much better throughput with Intel-based Macs than with their PowerPC counterparts.
MacFixIt reader Dave Buffington writs:
"I'm using a Motorola 5120 cable modem...
"With my old iMac G5 1.8 Ghz, CNET's 'Bandwidth Meter' routinely reported connection speeds of 1200-1400 kbps.
'Now, with my new iMac Intel Core Duo 2.0 Ghz, CNET's meter routinely reports connection speeds from 4000-4500 kbps."
Feedback? Late-breakers@macfixit.com.
Previous coverage:
Resources