Improved WiFi Performance

One of the more notable changes in the 2011 MacBook Pro lineup is a completely different WiFi chipset and subsequent RF design. The previous 2010 MacBook Pro included 802.11a/b/g/n support using a BCM4322 which included full 2x2 MIMO support, meaning two spatial streams were supported. Bluetooth 3.0 was provided by a BCM2070, and the whole solution was simply a BCM954224HMB reference design.


2011 MacBook Pro WiFi+BT Module—Courtesy iFixit

Back when the new Airport Extreme (Simultaneous Dual-Band II) launched, it included one little-hyped feature. One of the most notable improvements over the previous design was inclusion of a full 3x3 radio—again 3 spatial stream support. At the time, there were no Apple products that could actually use 3 spatial streams, and as a result many assumed the feature was completely locked down.


My wall-mounted Airport Extreme (Simultaneous Dual-Band II)

The Airport Extreme has had 3 spatial stream support for a long time to little fanfare. The Airport Extreme still only allows 20 MHz channels on 2.4 GHz spectrum. Other WiFi AP vendors ship firmware which will automaticaly selects 40 MHz channels on 2.4 GHz spectrum per WiFi Alliance rules, but Apple uniformly uses 20 MHz channels on 2.4 GHz. It's a design choice Apple made a while ago which still exists to this day – for two reasons. The first is that it prevents you from being, well, less than courteous and eating up to over 80% of spectrum on the already crowded 2.4 GHz ISM band with one AP. Apple's rationale for disabling 40 MHz channel support on the 2.4 GHz spectrum (for both clients and APs) is that Bluetooth needs lots of bandwidth to hop around on, and already a wide variety of Apple desktop and notebook products come by default with Bluetooth peripherals. Maintaining a good A2DP stereo stream for example requires considerable 2.4 GHz bandwidth. Instead, if you really want 40 MHz channels Apple recommends using 5 GHz, which Apple clients and Apple APs both allow to work with 40 MHz channels.


2011 MacBook Pro WiFi+BT Module—Courtesy iFixit

The 2011 MacBook Pro refresh is the first line of Apple products to bring 3x3 radios that can finally enable faster transfer rates and better performance at the edge of WiFi range. 3x3 MIMO support is starting to become relatively common in the PC notebook space, but this is the first for Apple. Inside the 2011 MacBook Pro is a BCM4331 and three clearly U.FL antenna connectors (on the left) for WiFi, as opposed to two in the previous design.

The fourth on the right is for Bluetooth, which remains 3.0 and provided by the same BCM2070 as previous models. Interestingly enough, though the Bluetooth controller is the same, the 2011 MacBook Pro includes newer firmware (37 vs 20), and software (2.4.3f1 vs 2.3.8f7). Hopefully at some point the older design will see a firmware update and bring whatever changes and improvements were made. Though the software versions are different, we couldn't detect any notable differences between the two in practice.


Left: 2010 MBP Bluetooth Hardware, Right: 2011 MBP Bluetooth

However, there's a dramatic improvement in both WiFi range and performance between the 2010 and 2011 refresh. With 400 ns guard intervals 40 MHz channels, 64-QAM modulation, each spatial stream adds n*150 Mbps. With 20 MHz channels, it's 72.2*n Mbps. For example, 1 spatial stream has a data rate of 150 Mbps, 2 has 300 Mbps, 3 has 450 Mbps, and so forth all the way up to 4 spatial streams and 600 Mbps as defined in the 802.11n specification. The reality of the matter is that what physical layer rate you'll see depends on the modulation and coding scheme and how many streams are going. You can look those up at any time by holding option and clicking the WiFi indicator, and looking them up in a table.

We tested a 15" 2011 MacBook Pro alongside a 15" 2010 MacBook pro connected to an Airport Extreme (Simultaneous Dual-Band II) running latest firmware. I originally suspected that 3 spatial stream support wasn't enabled, and that Apple would push a firmware update out right after their first 3 spatial stream products started shipping. Interestingly enough, it's always been there, enabled, this is just the first client I've gotten my hands on that does it. I'm not a huge fan of the Airport Extreme (I use a WRT54G-TM with Tomato and a WRT-600N with DD-WRT), but it's the only thing on hand with 3x3 MIMO. I tested in four different locations in my house—in my office, living room, kitchen, and outdoor patio. The base station is in my office mounted on the wall close to the ceiling, and those locations are subjectively ordered from best to worst.

To test, I initiated a large transfer over SMB (from a Windows Server 2008 R2 install with a 5 TB RAID5 array connected over gigabit ethernet) on each client, continually pinged AT, and at each location checked the reported transmit rate and RSSI. What we're reporting here is again the physical layer link. I'll show in a second that real-world transfers also improved, this just gives some perspective for what raw link rates are being negotiated at each location.

WiFi Transfer Rate Differences—802.11n
  2011 MacBook Pro 2010 MacBook Pro
  RSSI Transfer Rate (Mbps) RSSI Transfer Rate (Mbps)
Location 1—Office -44 450 -42 300
Location 2—Living Room -61 130 -64 117
Location 3—Kitchen -69 117 -68 78
Location 4—Outdoor Patio -85 20 -84 13

In most cases, RSSI is within the margin of error. RSSI is generally not something you can compare, but since both wireless chipsets are Broadcom and the numbers are so close, it seems they're reported the same way and probably just dBm. Just know that generally it doesn't work that way unless you're lucky. What's important, however is that the negotiated link speed is noticeably better in essentially all locations on the new 2011 MBP. Even when the extra antenna isn't being used for a spatial stream of its own, it's actively improving link quality and helping the new MBP negotiate higher physical layer speeds.

So how much of a difference does 450 Mbps 3x3 make over 300 Mbps 2x2? With both in the exact same spot in my office, I saw throughput of 98.1 Mbps on the 2010 MBP compared to 113 Mbps on the 2011 MBP. The modest 15% improvement over the previous generation's wireless chipset isn't dramatic, instead the dramatically improved range is.

110.28 Megabits/s over WiFi. I later saw sustained 113 Megabits/s.

Subjectively, I found many more APs visible with the new MBP. I was able to cling onto my AP all the way out to the curb (just like smartphones) when connected on 2.4 GHz, something the old generation just couldn't do.

The only complaint I have about the new wireless chipset is that it seems to hunt around for what rate it wants negotiated. I saw a number of different MCS (modulation coding scheme) values with the 2011 MBP in the exact same place. Link rates from just below 300 Mbps all the way up to the expected 450. It seems to settle out at the expected 450 Mbps in the same room as the AP, it just takes a while, whereas other 2x2 stacks I've seen always lock onto 300 Mbps and stay there in the same room and position.

Display Quality Thunderbolt
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  • jb510 - Friday, March 11, 2011 - link

    It would seem to me their is one currently shipping Thunderbolt periphral... A 2011 MBP in target disk mode. Maybe you could drop an SSD in one and do some preliminary testing? Reply
  • jb510 - Friday, March 11, 2011 - link

    damn... wish i could edit that comment originally typed on my iphone... but their doesn't appear to be any way... (misspelling repeated for comedic effect) Reply
  • deadshort - Friday, March 11, 2011 - link

    Thanks for the genuinely informative review. Running both low-load and high-load battery tests is especially helpful to developers, etc.

    One question. You chose the 2.3Ghz/8MB cache system. Was that just 'cuz you swing that way, or do you expect significant performance benefits for some workload you care about? For these machines is it a 10% price goldplate, or a reasonable increment to keep these CPUs fed? I am seriously interested....
    Reply
  • Brian Klug - Friday, March 11, 2011 - link

    I can speak for myself at least, but part of the reason for the 2.3/8 MB system choice was that it's the only preconfigured (Apple Store available) configuration that comes with the anti-glare display.

    Essentially, if you're a customer walking into the apple store and don't want the glossy/glare display, you're immediately forced into buying the highest-specced (and most expensive) MacBook Pro. It's frustrating because the only way to get lower specced systems is BTO online.

    Obviously we got these systems on launch date to immediately start working, and that was the reason for the 2.3 choice.

    -Brian
    Reply
  • synaesthetic - Friday, March 11, 2011 - link

    You know, I don't get this thin crap. I really don't.

    I mean, I can understand it. From a purely aesthetic point of view. Sort of, anyway.

    I'm sick of "thin" gadgets with weak performance and fragile builds. Thick gadgets means more tech fits inside. My HTC Glacier is quite thin, and you know what? I wish it was thicker. It'd be easier to hold onto, and HTC could have put a bigger battery in it!

    Stop making things so stupidly thin. Instead of driving the miniaturization of components on "thin," why not take that same miniaturization power and make things a bit thicker... with more power/cooling/battery inside?

    Thin may be sexy, but powerful is even sexier!

    Then again, Apple's never really cared to broadcast the specs of their devices, hoping instead to gloss over it to such a degree that nobody questions paying ridiculously inflated prices...
    Reply
  • Marc B - Friday, March 11, 2011 - link

    I am finally buying my first MacBook this year, and I am 70/30 leaning toward the 15" MBP. The 17" version has the high res screen and express port, but the 15" MBP is lighter/smaller and has the SDXC reader. Will the Thunderbolt port will provide enough throughput to allow simultaneous in/out?

    I am using this to log HD video on location, and was wondering if the express port is no longer necessary to use with a small ESATA array now that you can have high speed storage in and out using the Thunderbolt port.
    Reply
  • Belard - Friday, March 11, 2011 - link

    If Apple is pushing their notebooks to be more and more Desktop replacements...

    Where is a docking bay to handle all the connectors? How hard for a single connector to handle everything?

    Lenovo sells about 3 different Docking units $130~300 for their regular Thinkpad line (ie: NOT Edge or L/SL series).

    We have a few users who use them. Comes to the office, drop the notebook into the dock and turn it on, not a single cable to be attached. They include 4 USB ports (or more), PS/2 ports, HDMI and DVI ports, Ethernet and of course charge up the battery.

    So one user would have to plug in 7 cables everyday if he didn't have a dock... like his keyboard, wireless desktop mouse, 21" display, various printers and devices, etc.
    Reply
  • name99 - Friday, March 11, 2011 - link

    " I still haven't figured out how to actually grab SINR out on here, all I can see for the moment is just RSSI. "

    Apple's Airport Utility does give you part of what you want.
    If you open it, go to "Manual Setup", see the summary page, and click on where it says "Wireless Clients: 2" (or 3 or whatever) you will be given a page that, for each connection, shows their signal and noise levels (along with a graph).

    Of course this doesn't exactly have any bearing on what we are discussing, because the numbers that are presented are the intermediate term SINR values, relevant to shadowing but not to fading. The numbers that are relevant to fading (and thus to MIMO tricks) change on a millisecond time scale, and so what one really wants is an indication of their standard deviation, along with other info like the connection diversity. This is all way more geeky than Apple (or any other consumer company) is going to provide.
    Reply
  • humunculus - Friday, March 11, 2011 - link

    Any chance you could run a few of the tests on the 2.0 and 2.2 GHz models. I am interested in how much performance difference there is between the 2.2 and 2.3 GHz 15 inch Macbook Pro models. It is hard to assess if the 10% cost increase is warranted. Thanks Reply
  • Belard - Saturday, March 12, 2011 - link

    The $400 price difference is for the extra 200mhz (Apple values that at $250 - these are notebook CPUs, so pricing from intel is a factor)

    And then $150 to sometimes double the performance of the GPU for games.

    Oh, and an extra 250GB of HD space (which is about $5 in the real world).
    Reply

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