New iMacs With P55 Chipset (i5/i7) DO NOT Support Jumbo Frames [Archive]

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tsugaru

Dec 2, 2009, 07:31 AM

Way to be Apple. Way to be. Skimping a few cents on an Ethernet controller for your higher end prosumer computers. The other iMacs released this cycle have NIC controllers with jumbo frames. Heck, even my original 20" 2.0GHz Intel iMac had jumbo frames, as did the gimped 24" iMac 2.66GHz 9400m I sold a few weeks ago.

Seems like with every iMac there's always a slight niggle that prevents it from being a perfect machine.

Aside from all the issues with mine (which will be rectified soon) and others, I'm forced to quote Nancy Kerrigan with a resolute "Why?"

edesignuk

Dec 2, 2009, 07:35 AM

I'm sure it matters to you, but really, this is the most consumer targeted computer Apple make. How many of them do you think know what a "jumbo frame" is and why would they care? I didn't know what it was, and I'm not a complete idiot with computers.

Bluegiz90

Dec 2, 2009, 07:38 AM

KentuckyApple

Dec 2, 2009, 07:44 AM

Just curious, but what kind of data are you working with that you need to use jumbo frames?

AdeFowler

Dec 2, 2009, 07:45 AM

Whats Jumbo Frame? :confused:

Something to do with Nelly the elephant I think ;)

Husker

Dec 2, 2009, 07:45 AM

not only do I not have the slightest idea what this thread is about...but quoting Nancy Kerrigan? Seriously?

tsugaru

Dec 2, 2009, 07:54 AM

http://en.wikipedia.org/wiki/Jumbo_frames
http://www.smallnetbuilder.com/content/view/30201/54/1/1/

To quote that in English, from my NAS (read: network storage) I would get around 33-42MB/s download speed and 18-22MB/s upload.

Now on this machine, most I will get is 16-23MB/s download and 14-16MB/s upload.

Many people bought this machine so that waiting for operations to complete would be reduced. For some stuff, it's going to be slower.

KentuckyApple

Dec 2, 2009, 08:19 AM

What happens when you increase the MTU? What size are you trying to use?

tsugaru

Dec 2, 2009, 08:28 AM

What happens when you increase the MTU? What size are you trying to use?

I use 9000, as all my other stuff supports it.
On the i7, You can't increase it, whether it's through the network pref pane, or via sudo ifconfig en0 mtu x.

It's due to the NIC/PHY. The ones on the LGA775 based iMacs (Core 2s) use a PHY that allows for jumbo frames. The LGA1156 based iMacs (Core i5/i7) do not.

There is a discussion of this on the Apple forums.

http://discussions.apple.com/thread.jspa?threadID=2236017&tstart=0

knewsom

Dec 2, 2009, 09:06 AM

I wonder if this is something that will be fixed with a firmware update. That's a pretty major problem.

Now I'm glad I bought a DROBO instead of a fast NAS.

tsugaru

Dec 2, 2009, 09:19 AM

I wonder if this is something that will be fixed with a firmware update. That's a pretty major problem.

Now I'm glad I bought a DROBO instead of a fast NAS.

Firmware will not fix it.
It's a hardware issue.
http://www.broadcom.com/collateral/pg/5764M-PG100-R.pdf
See page 4.

To relate it for those who are like 'why is this a big deal?'
When you're transferring files consistently and have over 3TB of network storage with about 2TB full, the difference between 20MB/s and 40MB/s adds up quite quickly.
To put it on another level; if you bought a new car, and ponied up for air conditioning, would you want your power doors/locks taken away just because you upgraded?

edesignuk

Dec 2, 2009, 09:24 AM

To relate it for those who are like 'why is this a big deal?'
When you're transferring files consistently and have over 3TB of network storage with about 2TB full, the difference between 20MB/s and 40MB/s adds up quite quickly.
To put it on another level; if you bought a new car, and ponied up for air conditioning, would you want your power doors/locks taken away just because you upgraded?Fair enough. Most people won't know what "jumbo frames" are, but from what you say many will see the implications on them cheeping out with this. Apple bastids. :rolleyes:

tsugaru

Dec 2, 2009, 09:27 AM

Fair enough. Most people won't know what "jumbo frames" are, but from what you say many will see the implications on them cheeping out with this. Apple bastids. :rolleyes:

Agreed.

There are a bunch of people just looking for the basics (fast CPU/RAM, shiny screen, et al) but I know there's a bunch of us who like a little more. To be downgraded for going high end is kinda odd.

Tom Sawyer

Oct 29, 2010, 12:03 AM

I can confirm that the new 2010 models have the same limitation... no MTU higher than 1500. Very disappointing. :mad: