In our review of ASUS' Eee Pad Transformer Prime I mentioned that I couldn't sustain speeds greater than 2Mbps over WiFi on my review unit. In practice, most web pages loaded at a meager 0.5Mbps. ASUS insisted the problem was limited to my unit however CNet referred to a similar issue in their testing:

Unfortunately, during the review process, we experienced some very suspect performance issues (detailed below), which led us to believe we were possibly in possession of a faulty unit. So, we are going to hold off on giving final ratings for the Prime, but check out our initial impressions.
At the same time, I had test data from both ASUS and NVIDIA that show the Prime is capable of reasonable WiFi speeds. Yesterday morning I received a replacement Prime which was tested prior to being sent my way. The good news is the 2Mbps cap and poor range are both gone, the new sample is much faster on WiFi. Clearly there was something wrong with my original unit and it's being sent back to ASUS today for an autopsy. The bad news is I was still getting numbers around half of the original Transformer.
Using Ookla's web app I get a consistent 34 - 37Mbps on the original Eee Pad Transformer (our actual WiFi performance tests involve downloading a file from a local server, but Speedtest was a quick and easy way to verify the problem). My original Prime review sample averaged around 0.5Mbps, while the replacement Prime got around 10Mbps - all in the same test location. Fiddling around with location I could get the replacement Prime up to 16Mbps. My test area is riddled with challenging interference so I setup a separate test area in another room. Even after buying the same Netgear WNDR4500 wireless AP that ASUS verified 31Mbps+ operation on, I wasn't able to break 16Mbps.
I have four other APs covering my house, I turned all of the radios off as a last ditch effort. Boom - 36Mbps on the Prime.
The culprit appeared to be either my 3rd gen Time Capsule or 5th gen Airport Extreme, with those radios off and using the WNDR4500 I was able to get performance competitive to the original Transformer. Here's where things get interesting. The original Transformer was made out of plastic, through which RF travels quite nicely. The Prime's metal construction makes things a bit more finicky. Indeed this is exactly what I saw, where depending on tablet and AP orientation I'd see anywhere between 10Mbps and 36Mbps downstream (average speed tended to be in the 15 - 20Mbps range). Apple gets around this issue in the iPad by putting the WiFi antenna behind the plastic Apple logo, however it's not entirely clear to me where the WiFi antenna is on the Prime (I have this policy about not taking things apart until I'm done testing them).

As to why performance was lower with the Apple APs active, I'm not entirely sure. Chasing down RF interference issues can be a severe undertaking. One thing is for sure, the Prime is going to be far more finicky than its predecessor when it comes to reaching peak speeds over WiFi. 
WiFi performance isn't the only thing that improved with the new unit - I'm getting much better battery life as well. Our video playback battery life test doesn't have anything running in the background, but we are actively connected to a WiFi network throughout the duration of the test. As I surmized in our review, it's possible that whatever was causing the WiFi issues also had a negative impact on battery life. Curious to find out if battery life had changed as well as how the TF Prime did in its Balanced power mode, that's the first test I ran upon receiving the new review unit. Things are starting to look a lot better:

Video Playback - H.264 720p Base Profile (No B-Frames)

I'm running the new unit through the test in Normal mode as well, I'll have updated results there by the end of the weekend. Given the rush to get the initial review out, you can expect a followup (along with a video review) sometime next week. I'll be working on it as well as some HDD/SSD caching stuff all weekend.
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  • OCedHrt - Friday, December 2, 2011 - link

    From the new chart, there really isn't anything new that's meaningful. 11.07 hours on balanced, but that can't be compared to the 9 hours on normal except that balanced should be higher. It's very possible that the 1st sample would've gotten 11.07 hours on balanced as well?
  • 7Enigma - Tuesday, December 6, 2011 - link

    Exactly, and the whole reason I came to post a comment. Why the heck would Anand retest using a different power profile?!? In a week after doing many tests with different profiles I'd understand, but I find it very disingenuous to make it appear that the new unit is the main reason you got an additional 2 hours out of the charge. (even though you do mention nothing is running in the background during the video playback test, without doing the normal test how can we really be sure all is equal?)
  • tildeleb - Saturday, December 3, 2011 - link

    If you have "Use Wide Channels" or "Use interference robustness" turned on, turn them both off. They are located in Airport/Wireless/Wireless Network Options in Airport Utility. If you are using 2.4 GHz remember there are really only 2.5 non-overlapping regular channels and only 1 with wide channels.
  • cleverjaja - Saturday, December 3, 2011 - link

    $1300.00 usd quad core i7, 8gb memory, radeon 6750m 1gb, 8gb ssd/ 700gb hard drive. Less than 1 inch height. Wow!?!
  • Cerif27 - Sunday, December 4, 2011 - link

    Like a lot of people, I'm REALLY looking forward to this device and really don't want to wait for the THIRD generation. However, also like a lot of people, I'll be doing a heck of a lot of web browsing/streaming on the device. These new revelations are a huge let down. I'm really looking forward to your further updates on this problem. I've trusted you guys implicitly for going on a decade, thanks for the detective work. I'll be keeping my fingers crossed that the final production line of them doesn't have this problem because this is about as close to a deal breaker as it gets. Sad. Face.
  • CoryS - Monday, December 5, 2011 - link

    How come I can only see this update on my phones news reader, or a google search? Going to the home page on a PC only shows the original review, for me anyway.
  • vision33r - Tuesday, December 6, 2011 - link

    Since the TF Prime is already shipping in some parts of the world which means that some units will have the Wifi and battery issue.

    The TF I currently have does have the battery drain issue and it is very irritating. It is nowhere close to the advertised or tested numbers.

    The bottomline is these tablets are much cheaper than iPads so Asus is allowing more bad ones through.

    With Apple, if I receive a bad unit I can get one replaced on the spot but with these Asus units I have to go through Asus support and it is a lengthy return process.

    I think the TF Prime is a rushed device just to be 1 up on the competition just before the major quadcore designs are due out. In 3 months we'll be talking about the iPad 3 and Galaxy Tab 3 both will feature greater than 720p display, quadcore, and better performance. Galaxy Tab 3, we maybe talking about 2GHZ quadcore.
  • Disorganise - Wednesday, December 7, 2011 - link

    is there any technical reason why these devices couldn't run Windows? If I read correctly there's ARM-based windows 8 tablets planned - is that the same type of processor?
    I was pretty close to getting the original TF, but in the end had to plump for a laptop instead cos I needed a way to play wtv files natively (no time to convert files before heading OS).
    The Prime looks good assuming the wifi isn't unfixable, but I think it would even more attractive if could dual boot windows 8 when it comes out.
  • Alemiser - Thursday, December 8, 2011 - link

    You probably have already have this covered,. Just wanted to ask if wifi analyzer was used to see if there are channel conflict between the APs.
  • Horace44 - Saturday, December 10, 2011 - link

    Email update received today from NCIX regarding my pre-order:

    Unfortunately, we just received word that the ASUS Transformer Prime has been delayed worldwide and will most likely not be available before Christmas. ASUS feels the WiFi range does not currently meet their standards and has delayed all shipments worldwide. At the moment there is no ETA and no information on available quantities on the first batch.

    Looks like this Wifi issue was not just isolated to a few test units. Thanks Anandtech for bringing this issue to light.

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