ASUS ZenFone 2 - ZE551ML (64GB, Dual Sim, MicroSD) Full Review | Tek Syndicate


The conversation I really want to have about this phone is how much of a potential disruption the componentry in this phone can cause the world market on mobile phones. The x86 CPU & The off-contract price.

We’re reviewing the ZE551ML -- First and foremost this phone is powered by a 64-bit 2.3Ghz Quad-Core Intel Atom Z3580 CPU, and the first smartphone with 4gb of Dual Channel DDR3. It has LTE Cat4+, up to 250 megabit. This model also has an industry-leading 64gb of internal eMMC flash memory storage rated at a transfer speed of up to 160 megabytes per second.

I also want to talk about the overall responsiveness of the device, and the advertised 60ms touch response time. Though I think the HTC One (M8) was the first device to break the sub 65ms barrier on strictly touch response alone, the touch event + time to open apps still seems a bit laggy, to me, on Android.

While this is something that merits formal testing, I informally show what I did in the video above: Basically, I just setup two phones side-by-side and tapped the icons at the same time to launch Chrome, the Play store app, etc. The Zenfone 2 is astonishingly faster than the Moto X – even the Samsung Note 4 – and I suspect it is not just the touch delay at work.

Historically, the touch delay has been a problem for Android but as of early 2014 I was given to understand this problem was a thing of the past. This may be something else entirely – like a double-tap delay – but I can tell you not having whatever delay that is makes things feel different. This type of thing is something I see die-hard iOS fans harp on as I don’t believe this has been a problem for iOS. Because of this immediate response, the ZenFone 2 feels astonishingly fast.

The GPU is a 6430 PowerVR @ 533mhz. It ships with Android Lollipop and I was delighted to see that I can get OTA updates from Asus just fine. In fact, I had two right out of the box. The wifi is 802.11AC 1x1 operating at a speedy 433mhz and I can tell you downloads by wifi were speedy. The download speed on the large OTA updates from Asus approached ten megabytes per, which might be the fastest real-world wifi download on a phone I’ve ever seen.

There are two cameras – a 12.6 megapixel 4:3 aspect ratio with an f/2.0 aperture lens and a 4096x3072 capture size. The optics seem to be a 5-element setup from Largan. The sensor is a Toshiba Sensor. The flash is a dual LED flash but the LEDs have different color spectra in order to capture more realistic color tones. A really slick camera app is also bundled that lets you do a lot of cool stuff with the camera – mainly automatic HDR photos with something they call SuperHDR and high-res photos even in low light. All this is called PixelMaster 2.0.

The front camera is 5 megapixel and they also bundled some software that lets you take a panoramic selfie but I just don’t think I can bring myself to take a selfie to show you.

In testing the camera hardware was good, but not significantly better than other phones we’ve tested. It was certainly not a disappointment, but nothing spectacular either. The test video that we shot seemed to have excessive motion blur and the stabilization function did not seem to work as well as on other phones. Asus, Unleash this x86 beast and show us what it can do with real-time video processing! :)

The phone also has NFC, which we used to transfer the accounts, documents and other stuff from the Moto X – that was basically a flawless experience. Kudos there. I was surprised it worked so well. It also asked me to enroll for an Asus account, but this failed with Error 100 and I’m not sure why. However, it let me continue with the setup process. Later I received an email letting me know the Asus account was setup. This was a phone we bought from Amazon, so it must have been a problem on the server.

Physical inspection of the device is interesting. No buttons or anything on the sides, except one divot on the right side which is only a spot to unsnap the back cover. There is a button and headphone jack are on top of the device, and a USB 2.0 micro connector on the bottom of the device. The power button on top is not particularly convenient but it is possible to wake the device with a double tap on the scren, or by drawing gestures on the screen with your finger. A “C” drawn with one finger will, for example, wake the phone and run the camera app.

The phone is Dual Sim capable, and there is a spot for a MicroSD card, which is all located underneath the back. With the dual sim setup, the second sim is for phone calls and texts only; it is not capable of data. You can swap the sims around easily enough, but it can be challenging to remove the back. It does not come off easily.

It does not have wireless charging, but one can see the NFC sensor on the back of the cover in the video above. The back cover is quite sturdy and has an attractive brushed metal feel, though it seems to be some kind of metallized plastic. In the middle of the back is an oval silver rocker button; this is the volume control. At the bottom of the back is a cutout for the speaker. With the cover off, it looks as though the battery is only removable if one removes about a dozen Phillips screws.

It’s a beveled design like the Moto X or the Moto G, meaning that it is thicker in the middle than the sides. At the sides it is 3.9mm thick, but the phone feels large but sturdy in my hand. I find this design is easier to pick up from a flat surface and it seems to hide wear better.

On the front, there are three permanent touch buttons for back, home and context at the bottom of the screen. The front is certainly dominated by the display – 72% of the front surface area is display.

However, the display on the phone is probably the weakest link overall on the device. While the display is a 5.5 inch Full HD 1920x1080 display implemented with a gorgeous led-backlit IPS display, it’s dimmer than I’m used to and is a power hog. This phone has a beefy battery, though, to help make up for that. While I would happily pay $50 more for brighter and more power-frugal oLED display, I suspect that Asus knows their market segment. It is hard to really complain about this on a $300 phone. With the screen brightness maxed out, I could run the phone for a little less than one full day with my normal workload. If I practically ignored the phone and had little screen on time, but left my background processes running, I could get just about two full days of power.

The other complaint I have is that the case and screen pick up scratches easily. I had only had the ZenFone2 out of the box for about an hour before I noticed a few extremely fine scratches on the screen. I think they came from when I put the phone face down on my rubber mat, but I’m not sure. You will need a good case and screen protector.

There were no headphones or other accessories in the box, other than the charger. However, the charger that came with this phone rapid charges and can get to 60% charge in 39 minutes. The way this happens is by upping the USB voltage and amperage. Asus calls this BootMaster but this protocol seems to be compatible with the Qualcomm Quick Charge (QC) 2.0 spec, so use that if you don’t have your BoostMaster handy.

What about the bundled software? It’s a mixed bag. There are some genuinely useful bundled utilities from Asus, but there is also some bundled apps that are little more than crapware in my opinion. Thankfully, I was able to uninstall the software I did not want by simply removing it in the Apps area of settings. Do normal people need apps like “Dr. Safety” ?? I don’t want to be too acerbic about the bundled software since I was able to uninstall the apps, but it is a little disappointing without knowing the rationale.

After I captured (hopefully) enough footage for this review, I did make a change to the font size on the phone. No, I’m not talking about display settings “text size” option. The font size selector here ranges in size from “Geriatric” to “Professor Farnsworth.” Curiously, changing the font size to “Small” doesn’t reduce the amount of screen real-estate menu items take. Consequently, the email app will only show about 5 emails at a time. The same was true on my MotoX; this is not a problem with Asus’s default config. The fix here is to use ADB to modify the device DPI settings. You don’t usually need root to do this on Android 5.0+ devices. Once I did this, I had an extra column of icons on the home screen, and I had a much more reasonable font size. Surfing web pages and reading emails felt much less elderly and was overall a better experience.

One other thing about the software stack is that Asus has customized stock Android with something they call ZenUI. I was really worried about this. I dislike so strongly what Samsung has done with their TouchWiz Android customizations that I tend to only buy devices I can root in order to install stock Android. Though the bootloader on my device is at present still locked, it was easily rootable. I haven’t yet decided if I’m going to put stock android on here, but I suspect this phone will become a modder favorite because of the cost/benefit ratio here.

As such, ZenUI is not yet off-putting to me, and it has continued to work well even though I changed the display DPI settings. At least 50% of ZenUI seems to just be a high quality Android theme, plus obvious enhancement. They seem to have customized Android “The Android Way” without coloring outside the lines too much. In that regard, it seems well engineered so I am reserving judgement on this aspect of the software stack.


AnTuTu: 47817 (just behind the Galaxy Note 4, and a bit ahead of the OnePlus One)

3D Mark Ice Storm Unlimited: 20016 (overall)

The Implications

We don’t usually talk about price because the product videos have a long lifetime and price fluctuates. The current US Retail price is $299 for the model we are reviewing. There is also an alternative model with a 1.8ghz CPU, 2gb RAM and 16GB storage. The lesser model is likely to be completely fine for normal people at a cost of just $199. The costs here are likely to upset the applecart of established players in the phone arena. The pricing, and the fact that this phone is as good as it is while having an Intel x86 CPU in it should really be shaking up the industry.

Let’s talk more about that potential for disruption: That’s what you came here for, right? If you didn’t already know, the CPU in this phone is an Intel CPU and that’s unusual. It’s x86. It’s not ARM. Nearly all low-power portable devices today use ARM and nearly all desktop and laptop computers in use today use an x86 CPU. ARM is a RISC architecture CPU; RISC is short for Reduced Instruction Set Computing and, historically, this type of CPU has had limited, but simple, efficient and clean design for executing code. This type of CPU knows how to carry out a limited number of operations, or instructions, and complex operations need to be done with a long series of simpler operations. CISC, or Complex Instruction Set Computer, on the other hand, refers to the type of implementation Intel relies upon for their x86 CPUs. If you’ve got a complex operation to do, it’s implemented in hardware. Historically, that has meant that CPUs that need a lot of transistors to implement those operations in hardware. That means those CPUs generally have a lot more transistors than RISC type CPUs, and those transistors take power and effort to run, even when they’re idle. CISC is also the type of CPU that tends to require more R&D efforts for each iteration. The specific x86 CPU from Intel in this phone, for the first time, really demonstrates to me that the game has changed with Intel; Intel is finally actually viable in miniature, powerful low-power-usage use cases. It’s toe-to-toe with a flagship ARM cpu in the Samsung Note 4. To say that the implications of this are broad and deep blowing would be the understatement of the year.


This phone, while it’s not a flagship killer, is actually quite good. The Intel x86 CPU upsets the status quo, but it goes toe-to-toe with phones that are twice the price. It’s disturbingly good and has a lot of polish. The screen is high quality, but seems to require a lot of power to run. While the large battery offsets the screen’s power requirements, a more efficient display could have provided exceptional battery life. The parts of the software that could be better can mostly be fixed by the owner. Overall, the device is good enough that I would feel ripped off ever paying $500-$600-$700 for a phone ever again. In benchmarks, this phone was quite close to the Note 4 which costs $700 (if you buy it from Verizon, for example). In using it side-by-side with the Note 4, it was obviously faster and more responsive in many ways.

I’m always delighted to witness the game changers in markets; this is one. It’s not perfect and the durability could be better, but for $299 it’s pretty great.

What are your thoughts on this device? Do you see it as a disruptive influence to the status quo in this market? Why or why not?

This is a companion discussion topic for the original entry at

Wow, great timing with this review. I'm in the market for a good quality budget handset. I've not finished the review yet but looks really indepth.
Keep up these kinds of reviews, love them

I had this phone for a week and I can't recommend it. Yes, it surely can be a nice thing to fiddle around with x86 on a phone. But strictly as an android phone it has some major drawbacks even in it's own price bracket.

  • The back is the cheapest feeling plastic I have ever encountered on a phone
  • The screen is ok but not great. Take a look at it from an angle and it looks like a cheap TN.
  • It is big and heavy. I would not want that in my pocket all day.
  • Bloatware! Tons of it.

And the list goes on....

Sure, if it were cheaper than everything else, it would be ok. But it isn't. Other phones have more style, quality, in a better form factor and for less or the same money. The best example for that is the OnePlus X. That is the phone I am using every day and it is all I need. 5" AMOLED, my favorite size for a phone, 3GB RAM, Dual Sim/MicroSD, no bloatware, dark theme and build quality that is outstanding for the price.

I have the newer ZE551KL, which does have the laser auto focus. It's a fairly good phone. Roughly the same price of the Base Zenfone 2. I'll add my additions a little later.