2 Replies Latest reply: Sep 23, 2012 10:08 AM by MarcusV24
MarcusV24 Level 1 Level 1 (0 points)

Why is it not possible to change MTU size to more than 1500? Buying such a high quality product, I would expect that it supports jumbo frames!

 

My NAS supports jumbo frames, the Air Port Extreme does but a brand new iMac doesn't???

 

 

Is there any patch or somethin to fix this?

 

Thanks!!!


iMac, OS X Mountain Lion (10.8.2)
  • 1. Re: Why does iMac (Mid 2012) not support Jumbo Frames?
    BDAqua Level 10 Level 10 (116,480 points)

    Hi Marcus,

     

    I find conflicting info on this...

    The Ethernet port supports the configuration of Ethernet frames larger than 1,500 MTU (Maximum Transmission Unit).

    http://support.apple.com/kb/HT4619

    Can anyone confirm if the new 2011 imacs already support jumbo frames? I heard it now uses a new broadcom ethernet chip that now supports jumbo frames on the 21 inch model. They removed jumbo frames support in the previous i5 and i7 models...

     

    Hmm, I remember that the iFix tear down revealed that the 2011 iMacs had a Broadcom BCM57765B0KMLG Eithernet chip. (just go to the page and if you are using safari/firefox press command + F and type "Broadcom" to jump to that particular)

     

    http://www.ifixit.com/Teardown/iMac-...eardown/5485/2

     

    so I did a little googling and found out that:

     

    http://www.broadcom.com/products/Eth...lient/BCM57765

     

     

     

    Integrated 10/100/1000BASE-T transceiver with:
    - 10/100/1000BASE-T triple-speed MAC
    - Compliant with IEEE standards
    - Compliant with IEEE 802.3az draft standard for Energy Efficient Ethernet™ (EEE)
    - State-of-the-art physical layer interface that exceeds IEEE requirements
    - Jumbo frame support with up to 9.6 KB frame size
    - EthernetAV protocols with IEEE 802.1AS, 1588-2008, IEEE P802.1Qat and IEEE P802.1Qav support

     

    So it should support Jumbo Frames.

    http://www.philmug.ph/forum/f23/new-imac-early-2011-sandy-bridge-processors-7106 4/index8.html

     

    Originally Posted by mpe View Post

     

    At least mine doesn't

    Weird. My 27" 3.1GHz iMac that was delivered yesterday supports jumbo frames fine. I was quite concerned that it wouldn't because I rely on them for good performance with my NAS

     

    I set it using System Preferences -> Ethernet -> Advanced -> Ethernet -> Configure Manually.

    I've confirmed the setting by checking the output of ifconfig. It shows an mtu value of 9000.

    http://forums.macrumors.com/showthread.php?t=1148176

     

    Some of the 2010 iMacs did not I read.

  • 2. Re: Why does iMac (Mid 2012) not support Jumbo Frames?
    MarcusV24 Level 1 Level 1 (0 points)

    Hi BDAqua!

     

    Thanks for your fast and detailled reply!

     

    I'm sorry, I expressed myself not clearly - I was talking about the WiFi Interface, not the LAN Interface.

     

    LAN Interface does support Jumbo Frames, but the W-LAN doesn't.