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New iMacs Ethernet (NIC) Jumbo Frames?
- Thread starter urbanmacUser
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Yeah. It's a bummer. No jumbo frames on my 2010 i7. I can see a mild speed hit when accessing my NAS versus when both are set for jumbo frames. Had to put the NAS back down to MTU default (1500).
Apple needs a new Broadcom driver to support Jumbo Frames
I have a 17" i7 MacBookPro (Mid 2010 Unibody) which uses a Broadcom 5764 gigabit chip for its cabled ethernet interface. There appears to be no Jumbo frame support in this kernel extension/driver - kext (1500 MTU max). I have a 15" Macbook Pro (non-unibody) and a Mac Mini both use a Marvell Yukon 88E8055 gigabyte chip for their cabled ethernet interface and they have Jumbo Frame support (9000 MTU and down) as they should. Lack of Jumbo Frame support is causing my backups and other copies to run much longer then they did on my old 15" MacBook Pro. I have opened a case with Apple Care to get issues escalated to engineering since the chip is clearly capable of Jumbo Frame per Broadcom's site. All systems are running Mac OS X 10.6.4. If you have Apple Care and your Mac has a broadcom 5764 gigabit chip and no Jumbo Frame support I suggest you also open a case. It is the Sata driver issue for the unibody MBP only running 1.5 vs 3.0 again.
I have a 17" i7 MacBookPro (Mid 2010 Unibody) which uses a Broadcom 5764 gigabit chip for its cabled ethernet interface. There appears to be no Jumbo frame support in this kernel extension/driver - kext (1500 MTU max). I have a 15" Macbook Pro (non-unibody) and a Mac Mini both use a Marvell Yukon 88E8055 gigabyte chip for their cabled ethernet interface and they have Jumbo Frame support (9000 MTU and down) as they should. Lack of Jumbo Frame support is causing my backups and other copies to run much longer then they did on my old 15" MacBook Pro. I have opened a case with Apple Care to get issues escalated to engineering since the chip is clearly capable of Jumbo Frame per Broadcom's site. All systems are running Mac OS X 10.6.4. If you have Apple Care and your Mac has a broadcom 5764 gigabit chip and no Jumbo Frame support I suggest you also open a case. It is the Sata driver issue for the unibody MBP only running 1.5 vs 3.0 again.
I have a ReadyNAS NV+ and with jumbo frames I get relatively decent transfer rates over AFP, 30MB/s or slightly faster with my older C2D Extreme iMac. The new i7 is really slow, and seems more like 100Base/T speeds.
I need to play with the settings of everything a bit more, but this limitation is really irritating.
The imac 21 i3 in my office has BCM5764 (device id: 0x1684) which supports jumbo frame.
http://www.broadcom.com/collateral/pg/5764M-PG100-R.pdf (in the pdf is states BCM5784 doesn't not support jumbo frame).
Kext name is showing as BCM5701 which also supports jumbo frame.
http://www.broadcom.com/products/BCM5701
Nevermind, i see it, 5764M does NOT support jumbo frame.
http://www.broadcom.com/collateral/pg/5764M-PG100-R.pdf (in the pdf is states BCM5784 doesn't not support jumbo frame).
Kext name is showing as BCM5701 which also supports jumbo frame.
http://www.broadcom.com/products/BCM5701
Nevermind, i see it, 5764M does NOT support jumbo frame.
I'll guess that the pullback from jumbo frame support was deliberate and was done to reduce compatibility problems with less capable hosts, routers, and switches.
It could be worse. In the early days when all Ethernet was coaxial thick Ethernet with vampire taps, the speed limit was 1.5 Mbps and the 1,500 MTU limit was more than big enough. And that speed was six times faster than the AppleTalk net I was using in my lab back in the 1980s.
It could be worse. In the early days when all Ethernet was coaxial thick Ethernet with vampire taps, the speed limit was 1.5 Mbps and the 1,500 MTU limit was more than big enough. And that speed was six times faster than the AppleTalk net I was using in my lab back in the 1980s.
New iMacs Ethernet (NIC) Jumbo Frames
OK, The latest info I have is that the current selling MacBookPro and iMacs use the same Broadcom 5764 chip which either the driver/kext does not implement Jumbo Frames (9000) for this chip or the chip does not support Jumbo Frames (9000) can't get a straight answer from Apple or Broadcom (waiting from a call back from Apple Care who escalated the question to engineering). The new Mac Mini uses a different Broadcom chip which DOES support Jumbo Frame (using same driver/kext). For MacBook Pro 17" users you can purchase an ExpressCard Adapter that supports Jumbo frames like the LinkSys EC1000 Gigbit ExpressCard Adapter which uses the same Marvell Yukon chip the previous MacBook Pro (non-Unibody) and MacMini used.
I don't know which network chip the pre-i5/i7 Unibody used for the ethernet connection.
So I found a work around for my problem with the LinkSys ExpressCard but I hope Apple just made a honest mistake like the SATA driver issue and not cutting cost because they think no one would notice and no ones use it sort like the Express Card slot on the 15" Unibody that was removed to add an SD slot instead of just putting an SD slot converter in the ExpressCard slot which would have been a more elegant solution becuase there are lots of use that do use the ExpressCard slot. So we will see.
OK, The latest info I have is that the current selling MacBookPro and iMacs use the same Broadcom 5764 chip which either the driver/kext does not implement Jumbo Frames (9000) for this chip or the chip does not support Jumbo Frames (9000) can't get a straight answer from Apple or Broadcom (waiting from a call back from Apple Care who escalated the question to engineering). The new Mac Mini uses a different Broadcom chip which DOES support Jumbo Frame (using same driver/kext). For MacBook Pro 17" users you can purchase an ExpressCard Adapter that supports Jumbo frames like the LinkSys EC1000 Gigbit ExpressCard Adapter which uses the same Marvell Yukon chip the previous MacBook Pro (non-Unibody) and MacMini used.
I don't know which network chip the pre-i5/i7 Unibody used for the ethernet connection.
So I found a work around for my problem with the LinkSys ExpressCard but I hope Apple just made a honest mistake like the SATA driver issue and not cutting cost because they think no one would notice and no ones use it sort like the Express Card slot on the 15" Unibody that was removed to add an SD slot instead of just putting an SD slot converter in the ExpressCard slot which would have been a more elegant solution becuase there are lots of use that do use the ExpressCard slot. So we will see.
I don't understand your question.
The chipset used on the i5/i7 iMacs unfortunately does not support jumbo ethernet frames. Gigabit ethernet with standard frame sizes is still of course supported. If you don't know what jumbo frames are, likely you do not need it.
http://en.wikipedia.org/wiki/Jumbo_frames
I think the poster was trying to quote a transfer rate.
24MB/s sounds like a typical speed for file transfer to a NAS. In my case, I went from roughly 40MB/s to 20MB/s when I upgraded my 2007 C2D Extreme iMac to the Mid 2010 i7 iMac. Jumbo frames helped me a lot.
Unfortunately the ultimate bottleneck in my case is the slow Sparc processor in the ReadyNAS.
Ah, that makes more sense. I get between 20-30MB/sec off my Drobo FS, averaging around 23MB/sec. Was closer to 30 consistently on my Mac Pro with jumbo frames enabled.
I have a 2010 i7 imac with a Broadcom 5764 and I don't think it supports Jumbo frames. If I go into the ethernet setup and go to manual it will not let me set MTU higher than 1500.
This disgusts me! When in this day and age that a brand new machine (flagship iMac) does not support that. I could understand it on the lower model iMacs to some extent. Thanks again Steve for cutting more corners for serious users and marketing a machine for teenagers to upload pictures easier to Facebook.
This disgusts me! When in this day and age that a brand new machine (flagship iMac) does not support that. I could understand it on the lower model iMacs to some extent. Thanks again Steve for cutting more corners for serious users and marketing a machine for teenagers to upload pictures easier to Facebook.
Some really good information here, though dated.
http://forums.creativecow.net/thread/8/1084302
Check out the last couple of posts on that thread.
http://forums.creativecow.net/thread/8/1084302
Check out the last couple of posts on that thread.
What is the purpose of putting Gigabit ethernet in these machines when you can't do better than 30-40MB/sec. Yes it's faster than fast ethernet, but a third of what we should be getting on GB ethernet.
Got everything I need in the network to have big data transfers and this macine won't do it. Was hoping to get about 100-110 MB/sec. to make backups and transfers quick.
Oh well
Got everything I need in the network to have big data transfers and this macine won't do it. Was hoping to get about 100-110 MB/sec. to make backups and transfers quick.
Oh well
The slow speed you are seeing in transfers is probably that the NAS is not fast enough to keep up with the gigabit throughput. We have 3 iMacs with the same chip and unfortunately also have the same issue with lack of jumbo frames. We have a QNAP 459 NAS and use dual gigabit with 802.3ad; so our file transfer speeds average around 100 MBps. So even though the iMac does not support jumbo frames you can still get good throughput as long as you have a sufficiently powerful nas and a decent switch. Our switch is GS108T.
I do have to say that I was disappointed by the lack of jumbo frame support. It seems to me this should be a standard feature on all gigabit adapters these days. I wouldn't expect such a cheap move on Apple's part, and I will be check the specs very closely before I decide to upgrade these. If I had got these to the office and my network hardware was not able to work around this limitation, Apple would taking return of 3 $7000 in used iMacs.
The NIC used in the iMacs are supposedly the "smallest" ever. (whether that's changed by now, I dunno).
So I can't imagine that being a "cheap move".
Sometimes there are unfortunate side effects to achieve something you want.