The first round of Ultrabooks were mostly underwhelming. It shouldn't be a surprise, but many of the efforts were just half hearted at best. Of the companies who shipped the first Ultrabooks however, it was ASUS who came the closest to perfection with the Zenbook.

ASUS' Zenbook embodied the form factor, portability and overall concept of an Ultrabook. Where it failed to deliver was with its keyboard, display and, at least initially, with its trackpad. The first Zenbook was an amazing effort given the short period of time that it was conceived and developed in, but it was too rough around the edges.

Despite only being introduced 7 months ago, the Zenbook is old news. This is the Zenbook Prime:

The Zenbook Prime is ASUS' second generation Ultrabook, built around Ivy Bridge silicon. Unlike most silicon updates to notebooks however, the Zenbook Prime takes an almost Apple-like approach to renovating the tangibles rather than just relying on a faster chip to do the heavy lifting.

I don't know that I've ever seen a faster turn around on implementing reviewer and user feedback into a product. The Zenbook Prime fixes nearly every issue I had with the original Zenbook. From keyboard to display, it's all significantly better with the Zenbook Prime.

The circumstances around today's launch are a bit peculiar. Intel has an embargo in place on the as of yet unreleased Ivy Bridge CPUs, this applies to both notebooks and desktops. One such line of CPUs, the dual-core ultra-low-voltage Ivy Bridge parts that will find their way into many Ultrabooks, is covered by the aforementioned embargo. That embargo lifts at some point in the not too distant future, but ASUS wanted to have its review-ready hardware out the door and getting coverage before then. Why the urgency? It could have something to do with Apple's expected launch of updated MacBook Air and MacBook Pro systems. Rather than for Apple to get all the glory for being first, ASUS set some guidelines: we're allowed to talk about everything to do with the new Zenbook Primes, we just can't get into specifics on the CPU just yet. That's right, you won't read any model numbers, clock speeds or cache sizes here. Given what's already public about the ULV Ivy Bridge lineup I suspect this information isn't too hard to figure out if you're really motivated.

Zenbook Prime (left) vs. Zenbook (right)

The rest of the Zenbook Prime has nothing to do with Ivy Bridge. The form factor of the Zenbook Prime remains unchanged from its predecessor. Just like before we'll see two distinct models, an 11-inch (UX21) and 13-inch (UX31) in for review. With the lid closed, these two look identical to their Prime-less (composite numbered?) counterparts. ASUS sent the 11-inch Zenbook Prime in for review:

ASUS Zenbook Prime Specs
	UX21A-DB5x	UX21A-DB7x	UX31A-DB51	UX31A-DB52	UX31A-DB71	UX31A-DB72
CPU	ULV IVB	ULV IVB	ULV IVB	ULV IVB	ULV IVB	ULV IVB
GPU	HD 4000
Display	11.6-inch 1920 x 1080 IPS		13.3-inch 1920 x 1080 IPS
Memory	4GB DDR3-1600 (on-board)
Storage	128GB U100 SSD	128/256GB U100 SSD	128GB U100 SSD		256GB U100 SSD
Wireless Connectivity	Intel Centrino N 6205, 802.11b/g/n 2.4/5GHz 2x2:2, Bluetooth 4.0
Battery	35Wh		50Wh
Camera	720p front facing
Audio	Bang and Olufsen ICEpower
I/O	2 x USB 3, 1x audio/mic, 1x microHDMI, 1x miniVGA		2 x USB 3, 1 x audio/mic, 1 x microHDMI, 1 x miniVGA, 1 x SD Card reader
Dimensions	299mm x 168.5mm x 3-9mm		325mm x 223mm x 3-9mm
Weight	1.1kg		1.3kg
Price USD	TBD	TBD	$1099	$1199	$1499	$1599

Pricing is still in the air as the Zenbook Prime won't be shipping until early June. I suspect much of how aggressive ASUS is on this front will depend on what Apple does in the coming weeks.

Introducing the UX32, Starting at $799

There's also a new member of the Zenbook Prime lineup, the 13-inch UX32. Featuring a thicker chassis, the UX32 will be offered as low as $799 with a 1366 x 768 TN panel, hard drive + SSD cache and as high as $1299 with a discrete NVIDIA GeForce GT 620M GPU:

ASUS Zenbook Prime UX32 Specs
	UX32A-DB31	UX32A-DB51	UX32VD-DB71
CPU	ULV IVB	ULV IVB	ULV IVB
GPU	HD 4000		NVIDIA 620M + HD 4000
Display	13.3-inch 1366 x 768 TN		13.3-inch 1920 x 1080 IPS
Memory	2GB DDR3-1600 (on-board) + 2GB or 4GB SO-DIMM
Storage	7mm 320GB HDD + 24GB SSD (cache)	7mm 500GB HDD + 24GB SSD (cache)	7mm 500GB HDD + 24GB SSD (cache)
Wireless Connectivity	Intel Centrino N 6205, 802.11b/g/n 2.4/5GHz 2x2:2, Bluetooth 4.0
Battery	48Wh
Camera	720p front facing
Audio	Bang and Olufsen ICEpower
I/O	3 x USB 3, 1 x audio/mic, 1 x HDMI, 1 x miniVGA, 1 x SD card reader
Dimensions	325mm x 223mm x 5.5 - ~9mm
Weight	1.44kg
Price USD	$799	$999	$1299

Depending on how well the SSD cache works, and how good the 1366 x 768 panel is, the $799 UX32A could be a very compelling system.

The Zenbook Prime Exterior

The all-aluminum Zenbook chassis makes another appearance with the Zenbook Prime. It's the same thickness and weight as its predecessor. The Prime also features the same port configuration. On the 11-inch model you get two USB 3.0 ports (one on each side), a mini VGA out (with bundled dongle), micro HDMI out and shared audio/mic jack. The 13-inch model adds an SD card reader, while the thicker UX32 adds full sized HDMI and a third USB 3.0 port on top of that.

While the outside of the Zenbook hasn't changed at all, it's what's inside that's completely different. Both the UX21 and UX31 now feature 1920 x 1080 IPS panels. I'll get into the debate over the usability of such a high res on such an 11.6 inch display shortly, but at a high level this is just awesome. ASUS is finally putting the type of attention we've been asking for on display technology. The 1080p panel on the UX21 looks amazing and performs extremely well as you'll soon see. I can only assume the UX31's panel is similarly impressive.

What else got updates? The camera (now 720p), keyboard, trackpad, WiFi, USB 3.0 and power adapter, to name a few.

The New Keyboard

The keyboard is all-new on the Zenbook Prime. Although it doesn't look as stylish as what ASUS introduced in the original, the new keyboard is worlds better to type on. It feels almost identical (but not completely) to the MacBook Air keyboard, which in my opinion is a good thing. Finger fatigue is significantly reduced compared to the original Zenbook. ASUS claims 12% increased key travel compared to the predecessor which definitely contributes to a better typing feel.

The new keyboard (left) vs. the old keyboard (right)

The keyboard obviously looks very similar to Apple's chiclet as well and now features a LED backlight. There are three selectable brightness settings for the keyboard backlight (four if you count off), which you control via a keyboard shortcut (fn F3/F4).

A Much Improved Trackpad

The problematic trackpad from the original Zenbook was actually addressed mid-cycle last generation. ASUS switched to an ELAN trackpad that did away with most of the issues I encountered. Users who wanted the new trackpad could call, complain and should've been able to get their unit swapped out although there was never a formal replacement program. The Zenbook Prime uses the same trackpad, although this is my first personal experience with it in a Zenbook.

In short, it's much better than what I originally reviewed. Keeping one finger on the trackpad's left click area while you move the pointer is no longer an issue. The pointer will occasionally refuse to move but it's very rare and ASUS even ships software that lets you tweak the trackpad's sensor to better match how you use it:

Tap to click and actually clicking the trackpad are both non-issues again. Two finger scrolling as well as three finger forward/back gestures all work very well. Overall the experience is pretty good, albeit not quite perfect. It's likely the best ASUS can do without writing its own trackpad driver. At some point it may just come to that however.

An Updated Power Adapter

The 45W power adapter from the Zenbook gets a slight update as well. Remember the charge indicator that never turned off? Fixed. Also the somewhat worrisome power connector has been beefed up, it's a bit thicker and I'm less worried about it snapping off.

The old Zenbook power connector (bottom) vs. the new Zenbook Prime connector (top)

I shouldn't be surprised that ASUS fixed these things but it's just so rare that a company listens to feedback and acts appropriately in such a short period of time. I would still like to see a MagSafe clone and better cable management than a bit of velcro, although navigating around any associated patents there should be fun for ASUS' lawyers.

Vastly Improved WiFi

The original Zenbook featured a 2.4GHz Qualcomm Atheros AR9485 802.11b/g/n WiFi solution. Only supporting a single spatial stream the best sustained speeds I saw were around 5MB/s using 20MHz channels at 2.4GHz. The Zenbook Prime offers a considerable upgrade.

Now inside the machine is Intel's Centrino Advanced-N 6205 controller. The 802.11a/g/n controller adds 5GHz support and link speeds of up to 300Mbps. In practice I saw a doubling of performance under the same conditions as the original Zenbook (80Mbps vs. ~40Mbps).

As a side benefit, since ASUS is using Intel's Centrino WiFi on an Intel platform it also by default supports Intel's Wireless Display (WiDi) technology.

Just like last time, the UX21A comes with a sleeve case, VGA dongle and USB to 10/100 Ethernet adapter.

USB 3.0 on Both Ports

Courtesy of Intel's HM76 chipset found on the Zenbook Prime's motherboard are the notebook's two USB 3.0 ports. The original Zenbook had a single USB 3.0 port and one USB 2.0 port by comparison. USB 3.0 performance is a bit higher than what I measured with the original Zenbook. I had no problems sustaining transfers at above 170MB/s.

VGA and HDMI out are also supported. There's no Thunderbolt or DisplayPort on the Zenbook Prime unfortunately.

Simplified SSDs

The original Zenbook offered one of two SSDs depending on the model you picked up: Sandisk's U100 or ADATA's SandForce SF-2281 based XM11. If you'll remember back to my review of the original Zenbook I expressed concern that ASUS was shipping a known buggy firmware with the ADATA drive, although admittedly I didn't run into any of the SandForce BSOD issues during my review of the system. It looks like those concerns can be put to rest as ASUS has dropped SandForce from the Zenbook Prime. Sandisk's U100 is all that's available now.

As we've alluded to in the past, the U100 isn't the fastest SSD on the block but it should be very well priced for ASUS and obviously faster than a mechanical drive. Read speeds are quite good, but write performance is where the U100 falls short. Do a lot of IO (e.g. install a game or just write sequentially to the drive) and you'll notice IO latencies increase. It's the same issue we ran into early on in the MLC client SSD space, but no where near as bad. The good news is there's no stuttering or other similarly undesirable behavior. The system still functions like it has an SSD, it's just that it could be a lot faster under load. I'm saving a full investigation into U100 performance for final Zenbook Prime hardware.

My hope is that we'll see vendors offer drop in replacements for the drive similar to what we saw OWC do for the MacBook Air. I still haven't gotten a straight answer as to whether or not the ASUS drive is electrically compatible with the MacBook Air SSD, nor have I been brave enough to risk nuking a drive to find out. Update: the two SSDs are physically similar, but not physically compatible. Here's a challenge to all SSD makers out there: build an upgrade kit for the Zenbook.

The Display in Pictures

The star of the show is obviously ASUS' 1920 x 1080 IPS display. Contrast ratio, viewing angles and color reproduction are all significantly improved compared to the original Zenbook. White is a bit warmer than I'd like by default (6014K) but otherwise I really have no complaints about this panel. It's easily the best display I've ever seen ASUS use and arguably one of the best displays ever deployed in a notebook, much less one as small as the UX21. Before we get to the actual numbers, here are some shots of the Zenbook Prime compared to the lackluster Zenbook display:

Zenbook Prime (front) vs. Zenbook (back)

Zenbook Prime (left) vs. Zenbook (right)

Zenbook Prime (left) vs. Zenbook (right)

Zenbook Prime (left) vs. Zenbook (right)

Note just how much better the viewing angles are compared to the old Zenbook panel. ASUS clearly got it right this time.

The Display in Numbers

The new 1080p panel looks good, but does it make any sacrifices in its performance? Thankfully, no. Max brightness is down a bit compared to the previous generation, but it's still higher than any of the portable Macs and much higher than your typical PC displays. Black levels are much improved over the original Zenbook as well:

The resulting contrast ratio is almost tablet-like:

It's not just the basics that ASUS delivers well on, color accuracy is top notch:

Color gamut is shy of the MacBook Pro but much better than the previous Zenbook and the MacBook Air:

Size is definitely an issue here. While I think the 1920 x 1080 panel will be a very good fit for the 13.3-inch UX31, there's a smaller subset of folks who are going to appreciate it in the 11.6-inch UX21. Personally I think it's fine but at 189 PPI the 11-inch Zenbook Prime is going to be a tough sell for those who have a tough time looking at small text.

Text on the 11-inch 1080p panel

ASUS' solution is to ship the UX21 with Windows set to 125% DPI scaling by default, unfortunately most applications (including many of Microsoft's own) don't deal with non-integer DPI scaling very well.

Here's what the default desktop looks like at 125%:

And here are examples of applications that don't behave well with Windows 7's DPI scaling:

In Skype, some text elements are tiny while others are huge. PCMark Vantage is an example of where you see this as well:

Here the scaled text actually can't fit in the area allocated for it, while the rest of the text is entirely too small.

There's not much you can do to work around this today with Windows 7. You're either going to have really small text or have to deal with funny scaling. This is unfortunately a major downside to not controlling the OS layer, ASUS is at the mercy of Microsoft to get scaling for displays with high pixel densities right. Windows 8 should be better in this regard but I ran out of time to try it out on the Zenbook Prime before the embargo lift.

The Test

To keep the charts clean and simple I omitted a lot of the config details of each of the notebooks. For your reference, here's the configuration of each of the notebooks in our tests:

 

Performance

As I mentioned earlier in this review/preview, the deal ASUS worked out with Intel prevents us for discussing clock speeds or specifications of the ULV Ivy Bridge silicon in the Zenbook Prime. Obviously the silicon is going to fit within the same 17W TDP as its predecessor so don't expect huge differences in clock speeds.

If you take into account Quick Sync and its SSD, the Zenbook Prime is an extremely quick solution. Looking at the breakdown of PCMark scores you get a much more realistic look at where the ULV IVB fits into things.

In some areas the Sandisk U100 holds the Zenbook prime back, here it's actually slower than its predecessor. Despite all of its issues throughout most of last year, SandForce was always fast.

I threw in a PCMark Vantage graph as we have a lot of older data in that benchmark that can help put things in perspective:

It's amazing the sort of performance gains we're able to show over the older Core 2 based ultra portables like the Dell Inspiron 11z and Adamo 13. Again we see a slight performance deficit versus the SandForce based UX21E.

GPU Performance

Peak synthetic GPU performance sees a sizeable boost compared to the previous generation Zenbook. 3DMark 11 requires DX11 hardware and thus the original Zenbook won't run on it, but the rest of the 3DMark tests give us some perspective.

Vantage shows us a 63% improvement over the HD 3000 based Zenbook UX21.

Here we see just how much better Intel's graphics cores have gotten over the years. The Inspiron 11z could barely run the entry level 3DMark Vantage suite, whereas the Zenbook Prime delivers nearly an order of magnitude higher score here.

Gaming Performance

We can say that the silicon in the Zenbook Prime's CPU features Intel's HD 4000, the upgraded 16 EU Ivy Bridge GPU. The result should be much improved gaming performance. Once again we are thermally limited so there are some cases where you won't see tremendous increases in performance.

At a high level, for any modern game, you shouldn't count on being able to run it at the Prime's native 1080p resolution. You need a discrete GPU (or Haswell) to pull that off. The former is a tall order for a machine that's already mostly battery. The good news is that 1366 x 768 is playable in many games.

Not all games will see huge performance gains, but the latest Batman title runs 30% quicker on the new Prime.

More CPU constrained and thermally bound environments won't show any improvement over the Sandy Bridge based Zenbook UX21.

The 61% increase in performance over the original Zenbook takes the Prime into the realm of playability at these settings.

Portal 2 is an interesting case as we are significanty CPU and thermal bound here. The Prime can reach frame rates as high as 39 fps, but after a couple of runs you see degradation into the 32 - 37 fps range. On average, there's no improvement in performance compared to its predecessor - there's no beating the laws of physics.

Diablo III

Last week Intel proudly showed me a demonstration of Diablo III running on Ivy Bridge's processor graphics, from a standard notebook all the way down to an Ultrabook. Eager to repeat the experiment myself, I fired up Diablo III on the Zenbook Prime.

Default settings at 1920 x 1080 were understandably unplayable. Dropping the resolution down to 1366 x 768 and clutter density down to medium however gave me an average of around 17 fps outdoors and 20 fps in early crypts. Given that Diablo isn't a twitch shooter, these frame rates were actually playable - all I needed was an external mouse.

As a primary gaming system, any Ultrabook this size is going to fall short. However, if you need to get your Diablo fix in while on the road, the Zenbook Prime will deliver in a pinch.

Battery Life

Generally speaking, the 11-inch Zenbook Prime delivers about the same amount of battery life as its predecessor. For some reason we're able to hit much longer idle battery life on the Prime than the original Zenbook although I'm still trying to find out why. There's also an 11% improvement in our x264 playback test, but on average I'd expect to see similar battery life to the Sandy Bridge model - just with better performance. Note that these results also come despite the fact that ASUS is driving a much higher resolution, and presumably higher power, display than the original Zenbook.

The Zenbook Prime bucks the trend Jarred saw with the first Ivy Bridge notebook review where battery life took a small step backwards. These results bode well for future Ivy Bridge notebooks and Ultrabooks. It still remains to be seen if Intel's 22nm process will actually give us a battery life advantage in any notebook compared to its predecessor. It's possible that we are seeing some of the benefits of 22nm here already and they are simply offset by the more power hungry display. With the move to 22nm Intel should have a better hold on active power and leakage, but it's always possible that we'll have to wait until Haswell for the process to really be exploited.

Just like last time, ASUS has a couple of widgets to quickly change between power settings. The instant on widget lets you switch between suspend to RAM and suspend to disk modes. The former is expected to deliver up to 2 weeks of standby battery life, while the latter can push up to 150 days. I didn't have the time to test these claims (life is short, I draw the line at spending it testing claims of 150 day standby battery life). ASUS once again includes a counter that estimates how long your system will last in either mode based on current charge levels and power usage.

The next widget is a quick tool to let you switch between high performance and battery saver Power4Gear power profiles. You can customize these profiles via the Windows control panel, but it's nice to have a button on the desktop that lets you quickly switch between them.

Configurable TDP

One feature of Ivy Bridge that we haven't been able to test until now is configurable TDP. While most Ultrabook CPUs ship with a 17W TDP, that's mostly an arbitrary thermal/power rating. If an OEM wants to design a chassis that can only accept a 13W part it previously had to hope that Intel would make such a thing. Alternatively, the OEM could underclock/undervolt a 17W chip on their own and hope to mimic Intel's validation and deliver a 13W configuration of their own. The former requires that a significant number of OEMs demand the part, while the latter is just too risky for the larger OEMs (get too aggressive on the undervolting side and end up with a bunch of unstable systems). The solution Intel proposed with Ivy Bridge is configurable TDP. For Ultrabooks this means you can set a 17W part to 13W.

Currently the setting is hidden away in Windows 7's power management settings. Once again I've had to censor the clock speeds here due to Intel's Ultrabook embargo:
You can map the 13W settings to the battery saver profile and then, at the click of a button, have a 13W Zenbook Prime instead of a 17W model. The difference in performance isn't significant however:

ASUS Zenbook Prime Configurable TDP Performance - Cinebench 11.5 (Multithreaded)
	16W - Max Freq	13W - Mid Freq	13W - Lowest Freq
ASUS Zenbook Prime UX21A	2.79	2.67	2.67

I'm still running battery life tests to quantify the impact on power consumption, but it's conceptually a neat thing to see in action finally. I suspect configurable TDP is going to play a major role with Haswell and convertible/dockable Ultrabook-tablet hybrids.

Thermals and Noise

As with most high performance notebooks that are this thin, cooling is difficult. Under load the fans in the Zenbook Prime are definitely audible, but in general ASUS does a better job cooling everything inside the Zenbook Prime than Apple does in the MacBook Air. I suspect much of this boils down to how aggressive Apple is about keeping fan speed/noise down compared to ASUS' desire to maintain a certain temperature level inside the chassis.

Final Words

With the exception of the SSD and Windows 7's unfortunate lack of elegant DPI scaling, the Zenbook Prime is the epitome of Ultrabook perfection. It has all of the build quality that we loved about the original Zenbook, with almost none of the quirks.

The display is truly in a league of its own. Color reproduction, brightness and contrast are all exactly where they need to be. Viewing angles are similarly perfect. While the original Zenbook's panel was frustrating, the Prime's display is wonderful to look at. Whether browsing the web or watching movies, it's just awesome. The biggest question is whether or not 189 PPI is too much for you. On an 11.6-inch screen I expect that not everyone will be fond of the resolution, but if you've wanted a ton of desktop space on a small display then the new UX21 will be everything you've been hoping for. I suspect more users will be happy with the 1080p IPS panel on the 13.3-inch UX31 however. I'll try to post an update in the coming days with some Windows 8 experience to see if that makes for a better fit. Kudos again to ASUS for working very hard to be competitive in this space, despite not having the purchasing power or control over the supply chain that Apple does.

The improved keyboard, is like night and day compared to the previous version - with a backlight to boot. The trackpad is also improved, although at the risk of overusing the Apple comparison I will say that it continues to be a hair behind what Cupertino has been able to deliver. The problem there is likely a lack of control over the software stack, a benefit reserved for vertically integrated companies.

Wireless performance and functionality are both improved over the original Zenbook and are, at least on paper, equal to Apple's MacBook Air. The move to a 2x2:2 802.11n setup with 5GHz support easily doubles WiFi performance compared to the original UX21. The use of Intel's Centrino Advanced-N WiFi stack enables WiDi support, which can be very useful on a notebook.

The convenience of two USB 3.0 ports, courtesy of Intel's HM76 chipset, is a welcome improvement as well.

Overall, I'm glad to see that ASUS is focusing more on the tangibles and user experience than just on shipping well engineered products. It's hilarious that out of all of the players in the notebook and tablet spaces combined, that ASUS seems to be one of the only ones (if not the only one) actually trying to go after Apple.

While I'll save the truly final verdict for when ASUS gets me shipping hardware, chances are if you've been waiting for the perfect 11-inch Ultrabook - the Zenbook Prime UX21A is it.