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i5 and i7 iMac Ethernet Controller Update

COW Blogs : walter biscardi's Blog : i5 and i7 iMac Ethernet Controller Update
We now have the actual product features page from the Broadcom 5764 Ethernet Controller that's now in the i7 and i5 iMacs. It's been said a photo tells a 1,000 words. I think this pretty much tells the story of the "i" line of iMacs.

Jumbo Frame Support - NO.

Without Jumbo Frame support, there's no way to connect to our Final Share SAN which is all ethernet based. No Jumbo Frame support, no professional video editing in our facility.

I've had all sorts of people write to me with various theories and ideas as to why Apple would take a part as simple as this and cut corners to make these the only products in their lineup that cannot support Jumbo Frames. It's pretty obvious to me that Apple either does not know about ethernet SAN or does not understand how it works. Integrating and promoting ethernet SAN based solutions would only make the iMac an even more attractive solution in the professional editing environment and promote sales. Connectivity to a large media array is the weak link in the iMac design. Ethernet SAN is the answer, but unfortunately, not in their latest and greatest machines.

So once again, if you're considering the 27" iMac know that you will be limited to just local FW800 storage with the i5 and i7 iMacs. A real shame and we'll be avoiding those machines unless Apple changes out the controller to make it Jumbo Frame enabled.

Posted by: walter biscardi on Mar 2, 2010 at 5:41:10 amComments (8) apple, final cut pro, imac, ethernet san, final share


Re: i5 and i7 iMac Ethernet Controller Update
by David Temmesfed
Do you know if they fixed this problem with the new 27" iMac that was release mid June?
@David Temmesfed
by Steve Modica
No. They are still using the same chip
replace ethernet
by walter biscardi
Not to mention your warranty would be voided instantly. We took delivery of the 3.33 Ghz iMac right before I left for NAB and I finally got it up and running this past Friday. It does work brilliantly with the ethernet SAN and I was able to set it up for Jumbo Frames the way we need it to.

The big difference between the i7 and the 3.33 Core Duo is the heat. The 3.33 runs incredibly hot compared to the i7. That's really the only difference I've noticed so far. Beautiful screen and it looks like so far this is the answer unless Apple decides to change out their controller on the iMac i7 and i5.

Anyone have a look at the newest MacBook Pro specs yet to see if it's the same Broadcom controller in there too? That would really suck.
replacing the controller
by Steve Modica
I haven't tried to open the thing, but I'm sure the imac has the controller soldered down. So replacing it would not be an option.
Replacing controller
by Allan Liang
Just throwing this out there, but would it be possible to open it up and somehow replace the controller? Or would this be impossible?
27"iMAC in my future????
by Joe Pitts
Thanks in advance Steve. i've been very hopeful in using these machines in a new build i'm setting up...hope it works

Doesn't sound too promising
by walter biscardi
I know you're "the man" when it comes to this stuff since Small Tree is the company that makes the magic happen with Ethernet SAN. In my own, humble year of working with this system, it's clear that everything has to work perfectly at all times in order for the system to be stable and reliable.

If anyone can make the i5 and i7 iMacs work with this, it'll be your company. I hope you can do it, but I'm definitely not going to be any sort of a guinea pig for this. I'd need to see it working for at least 6 months before I'd even consider putting something like this into a pro environment.

We're stepping back to the slower Core Duo 2 iMac because at least we know the ethernet controller will work out of the blocks.
Jumbos frames etc
by Steve Modica
Couple comments:

1. The imac can connect to the server. It just won't use jumbo frames. That forces the server to send 1500 byte frames which is harder and uses more cpu.

2. Apple's BCM 5764 supports LSO (large send offload) or TCP segmentation offload (same thing, different name). This let's the stack send large packets, and the card chops them up. This is a nice feature and is theoretically better than jumbo frames for transmit. (since the stack can send 32k or 64k rather than just 8k or 9k). Of course, all the *other* stuff on the network still has to deal with all the little packets including the switches and destination cards.

3. Some cards (like Small Tree PETG1NDA 10Gb card) support RSC. This is like LSO in reverse. You suck in tiny packets and aggregate them and make them into one big packet for the stack. This is a great feature, but the 5764 doesn't seem to do it. From what we can tell, no current gigabit chips do this. So on receive, the machine needs to work really hard to get all those packets processed.

4. The 5764 supports RSS (receive side scaling). This lets the chip segregate traffic into queues so it can be vectored to different cpus. Theoretically, this would let the imac handle the incoming packets with lots of different cpus, thus making up for no jumbo frames. However all of the incoming traffic is coming from one socket for AFP, so it's all going to one guy anyhow. Hence, probably not much benefit.

We're going to run some tests Friday and Monday and see what kind of numbers we get. We'll also try implementing LSO on our side and see if it helps. This will take a while.

Professional Video Editor, Producer, Creative Director, Director since 1990.

Credits include multiple Emmys, Tellys, Aurora and CableAce Awards.

Creative Director for Georgia-Pacific and GP Studios, Atlanta. Former Owner / Operator of Biscardi Creative Media. The show you knew us best for was "Good Eats" on the Food Network. I developed the HD Post workflow and we also created all the animations for the series.

Favorite pastime is cooking with pizza on the grill one of my specialties. Each Christmas Eve we serve the Feast of the Seven Fishes, a traditional Italian seafood meal with approx. 30 items on the menu.

If I wasn't in video production I would either own a restaurant or a movie theater.



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