Download rates

Question

Level 4

2,986 points

Download rates

I've noticed a consistent pattern in download rates on the Core Duo.

On my G4 PB when I download a large file from a site with consistenly fast servers, such as Apple, I get download rates that usually saturate at about 600 kB/sec on my cable modem. The rate will usually stay right there until the end of the download.

On the Core Duo, the rate oscillates. It peaks at 600 kB/sec and then a few seconds later drops to near zero and then peaks at 600 kB/sec. There period of this oscillation is about 7 seconds and this pattern repeats until the end of the download.

Both computers are downloading through the same Airport base station although not at exactly the same time. The net download time for the same file is about double for the Core Duo.

Anybody have similar or different experience?

- gws

iMac Core Duo, Mac OS X (10.4.4), 20"

Posted on Jan 27, 2006 7:09 PM

Reply

Answer 1

GW Schreyer Author

Level 4

2,986 points

Jan 27, 2006 7:42 PM in response to GW Schreyer

An update

I tried with both Camino and Safari on both computers, same story.

this only appears to occur with a wireless network. I moved the iMac to a location where I had a wired ethernet connection and then it had a good and consistent download rate.

I tried a direct file transfer via airport from one computer to the other. Each computer was connected to a DIFFERENT access point with a direct ethernet connection between the accesss points. I got the same oscillating type rate but the peak rate was about 2.5 MB/sec.

I tried a direct ethernet connection between the PB and the iMac. This time I had to find a file big enough to get a steady rate before it finished. An iMovie project was big enough. The rate peak rate was 27 MB/sec and was fairly steady.

It would appear that the Airport implementation on the iMac is having a little difficulty.

Reply

Answer 2

Jan 27, 2006 11:07 PM in response to GW Schreyer

Same story here. End results for me were choppy high-bitrate streams using Safari. I'll try streaming using wired ethernet when I get home.

Reply

Answer 3

Jan 28, 2006 1:54 PM in response to sesshomaru

Is your wirless router set to use any form of encryption (i.e. WEP or WPA)?

Reply

Answer 4

GW Schreyer Author

Level 4

2,986 points

Jan 28, 2006 1:57 PM in response to Patrick Ellis1

yes, WPA. However BOTH computers need to use the same encryption. Only the iMac is impacted.

- gws

Reply

Answer 5

Jan 28, 2006 2:03 PM in response to GW Schreyer

yes, WPA. However BOTH computers need to use the
same encryption. Only the iMac is impacted.

- gws

that may be the problem. I was experiencing incredibly pathetic internet access/download speed as well as local home network access with my new DC that was resolved when I disabled WPA. I'm not happy about it - a 5 year iBook and 1 year old eMac do not share that issue - so Im assuming that it has to do with the new wireless card being used.

I'll be playing around with various encryptions settings to see if I can make things functional and should also be sending off feedback to Apple about it.
Short of the wireless issue (and this one dead pixel that just showed up near the center of my screen), this Mac has been a charm.

Reply

Answer 6

GW Schreyer Author

Level 4

2,986 points

Jan 28, 2006 2:07 PM in response to Patrick Ellis1

it may be a WPA issues, it may not. however it doesn't matter much what the actual cause it, it doesn't work correctly.

I did submit a feedback note. Others that notice the same thing should also submit feedback. I doubt that a bug report from a single user can trigger action but similar reports from many users can.

- gws

Reply

Answer 7

GW Schreyer Author

Level 4

2,986 points

Jan 28, 2006 7:32 PM in response to Patrick Ellis1

I tried again with no encryption at all. No joy, same result.

- gws

Reply

Answer 8

Jan 28, 2006 9:58 PM in response to GW Schreyer

Similar situation here.

I noticed abnormally slow wireless download speeds when using WPA with TKIP encryption, but not with WPA-AES. It was repeatable. Also, a different computer using the same wireless settings and router works fine.

iMac Core Duo 20" and Dual G4 866 Mac OS X (10.4.4)

Reply

Answer 9

Jan 29, 2006 8:10 AM in response to brettbolt

Similar situation here.

I noticed abnormally slow wireless download speeds
when using WPA with TKIP encryption, but not with
WPA-AES. It was repeatable. Also, a different
computer using the same wireless settings and router
works fine.

iMac Core
Duo 20" and Dual G4 866 Mac OS X (10.4.4)

Unfortunately, my Belkin doesn't support WPA-AES so I'll just be reverting back to no SSID broadcast and enable MAC address filtering. Oh well....

Reply

Answer 10

steve_hy

Level 1

145 points

Jan 29, 2006 8:16 AM in response to GW Schreyer

I believe that this is all about the change in wireless chip from BroadComm to Atheros. I posted this query several days ago and it seems that what you are experiencing is idential to what I have experinced witht the Atheros chipset. Encryption does not affect this in any maeningful way;

I am about to purchase an Intel Imac but have a concern about the new Airport chip in these systems. Previous chips were Broadcomm and now the Intel systems have Atheros chips (as per ArsTechnica). On my PowerBook G4 and iMac G5 with Comcast broadband it regularly tests at 6,000+kbps download ( http://www.speakeasy.net/speedtest/). I also have a IBM ThinkPad T42p with the Atheros chip and the same Comcast test (at DSLReports.com) tests at 2,300kbps. All tested through Airport Express routers (Broadcomm chips).
Has anyone with Comcast or comparable broadband connections tested with their new Intel iMac?
All responses appreciated as I do not wish to duplicate my ThinkPad Atheros chip experinece with the new iMac.

Message was edited by: steve_hy

Reply

Answer 11

GW Schreyer Author

Level 4

2,986 points

Jan 29, 2006 8:22 AM in response to steve_hy

enough folks have responded with similar experiences that I guess that the thread is "solved" even though the problem is not fixed.

There is an issue, I will bug AppleCare some more to see if I can get them to issue a bug report. The first tech I called would not.

In the meantime, I recommend that everyone that is bothered by this submit feedback to Apple. Apple DOES read the feedback and enough of it might get their attention.

- gws

Reply

Answer 12

GW Schreyer Author

Level 4

2,986 points

Jan 29, 2006 12:52 PM in response to GW Schreyer

I've now got bunches of data that support the contention that the Airport implementation in the iMac Core Duo is hurting

see http://www.girr.org/macstuff/networkspeed.html

and look toward the bottom of the page

- gws

Reply

Answer 13

deivy

Level 4

2,365 points

Jan 29, 2006 7:06 PM in response to GW Schreyer

well, using the speakeasy site above, I was able to compare a G4 using a pci wireless card with an iMac DC.
This time, the G4 was faster by a factor of 1.1.
This, is far as I can see far from saying that the Airport card on the iMac has an issue.
Actually when I used <http://miranda.ctd.anl.gov:7123/>, I actually got faster speeds on the iMac.
By the way, this site gives you a lot of info that should be invaluable to debug your "transport" problems.

Deivy

Reply