It is important because Core-M was specifically developed for fanless tablets where silent operation, a thin profile, and low weight mattered. These chips had to dissipate as little heat as possible, and that meant running them at a very low default clock speed.

The Core-M chips in the original tablets were rated at just 4.5 watt Thermal Design Power. They could run at much higher turbo speeds, but only for a brief time. This made them suitable for low overall workloads, with just a bit of high load mixed in.

It's an interesting idea, but in our experience, Core-M chips were quite temperamental and you could never quite predict whether they would actually spool up to turbo speeds, or sit a particular assignment out. Not exactly what one needs out there in the field.

Dell apparently came to the same conclusion. Yes, tablets must be as think and light as possible, but not at the expense of consistent, reliable performance. As a result, Dell switched from 4.5 watt Core-M processor to "full" ultra-low voltage Core processors with a Thermal Design Power of 15 watts. All of these run at much higher default clock speeds, and if maximum performance is required, they can stay at full turbo speed considerably longer. That's because the tablets are built to handle the full 15 watts of heat, as opposed to just 4.5 watts with the Core-M chips.

But doesn't that mean much higher battery draw? Not necessarily. Intel has made significant progress in power conservation, and late generation mobile Core processors can have amazingly small power draws. The table below shows the five processors available for the Dell Rugged Extreme Tablet, with their major specs (see the full table here):

CPU Options
Intel	Core i7-8650U	Core i7-7600U	Core i5-7300U	Core i3-7100U	Core i5-6300U
Codename	Kaby Lake Refresh	Kaby Lake	Kaby Lake	Kaby Lake	Skylake
Cores/Threads	4/8	2/4	2/4	2/4	2/4
Lithography	14mn	14mn	14mn	14mn	14mn
Base Clock Speed	1.90 GHz	2.80 GHz	2.60 GHz	2.40 GHz	2.40 GHz
Turbo Speed	4.20 GHz	3.90 GHz	3.50 GHz	No turbo	3.00 GHz
Thermal Design Power (TDP)	15 watts	15 watts	15 watts	15 watts	15 watts
Windows 7 downgrade	No	No	No	No	Yes
Smart Cache	8MB	4MB	3MB	3MB	3MB
Integrated graphics	UHD Graphics 620	HD Graphics 620	HD Graphics 620	HD Graphics 620	HD Graphics 520
Graphics base speed	300 MHz	300 MHz	300 MHz	300 MHz	300 MHz
Graphics max speed	900 MHz	1,150 MHz	1,100 MHz	1,000 MHz	1,000 MHz
Intel vPro	Yes	Yes	Yes	No	Yes
Intel TSX-NI	Yes	Yes	Yes	No	Yes
Intel SIPP	Yes	Yes	Yes	No	Yes
Intel Trusted Execution	Yes	Yes	Yes	No	Yes

Interestingly, Dell picked their five available processors from three different generations of Intel Core processors. Why would that be? There is actually a very rational explanation.

At the low end is the Core i5-6300U. The chip was included because it's the only one that can (officially) still run the Windows 7 operating system that's still in wide use.

The Core i3-7100U is the only chip without turbo mode. This is suitable for applications where steady, predictable performance is the primary goal. No need for a turbo mode that may or may not kick in.

The Core i5-7300U and Core i7-7600U differ mostly in performance, which is likely about 10% higher in the 7600U. Core i5 and i7 chips often differ in specific Intel technologies, but that's not the case here.

On the high end is the Core i7-8650U from the Intel 8th generation "Kaby Lake Refresh" line. The big news here is that the 8th gen brings quad-core CPUs to the table. That's twice the cores and twice the threads of the other four chips. This brings up some questions.

Are four cores twice as good as two? The answer is, as in almost all things, "it depends." It depends on how much of a software application can be broken down into steps that can be run in parallel. If it's a lot, then a quad-core design might be considerably faster than a dual-core CPU.

But doesn't that also mean considerably higher power draw? Again, that depends. If a quad-core design runs at the same default clock speed as a dual-core system with the same architecture, then, yes, it'd draw much more power. So what did Intel do? They lowered the default clock speed of the quad-core chips by quite a bit. And, thanks to optimization in the 8th generation dye, managed to increase maximum turbo speed.

The result is that, theoretically, the quad-core i7-8650U can matches or exceeds dual-core performance just idling along and drawing not much power. But it has much higher peak performance.

In order to get a sense of the Dell Rugged Extreme Tablet's performance, we installed Passmark Software's PerformanceTest 6.1 that runs about 30 tests covering CPU, 2D graphics, 3D graphics, memory, and disk and then computes scores for each category and an overall PassMark score. We also ran our second benchmark suite, CrystalMark, which concentrates on single core performance. For comparison, we added the results of Dell's original Latitude 12 Rugged Tablet and three tablet competitors that we had also tested in the RuggedPCReview benchmark lab.

The other big problem makers of rugged Windows tablet face is that they also have to build this complex package so that dust and water won't get inside despite a whole complement of onboard PC standard ports, and so that things don't break or come loose when the device is dropped and rattled around. How did Dell go about making it all possible?

Well, they had a good base in the form of their existing Latitude 12 Rugged Extreme convertible notebook (see our full review), and that machine serves as the conceptual and general foundation for Dell's rugged tablet.

In essence, Dell condensed the guts of their convertible into a pure tablet form factor, retaining the same 11.6-inch display size and much of the functionality, but paring 40% of the weight and updating underlying technologies in the process.

That's not to say that the tablet and the convertible use the same internal layout. Tablets and convertibles are inherently different, with convertibles being two-box designs and tablets all-in-ones.

Unlike most mobile Windows systems, the 12 Rugged Extreme Tablet doesn't have any removable doors on its backside to provide access to RAM memory and internal expansion slots. So if you want to replace memory or one of the PCIe modules, or if maintenance becomes necessary, you have to take the tablet apart.

That's not terribly difficult. Undo a couple of dozen small Philips screws and the halves easily come apart. There are three ribbon cables between the halves and those always have fragile connectors, so care is advised.

The seal between the back and the front part of the housing — both made of impact-resistant, flame-retardant, fiber-reinforced PC-GF50(40) polycarbonate — is a hard plastic lip on the backside that presses onto a thin black rubber o-ring seal sitting in a channel on the front side. The o-ring seal is long and complex but seems replaceable. What's interesting here is that the seal doesn't just go along the perimeter of the tablet. Instead, it weaves in and out, protecting the electronics inside, but leaving anything I/O-related outside.

That's because it is quite difficult to properly seal standard PC ports and connectors. In most rugged devices those ports are not actually sealed to the inside. Instead, rubber plugs and hinged doors provide the protection. If one of them isn't closed properly, liquids can enter the inside of such devices. With Dell's design, it can't.

In the Dell tablet there are protective plugs also, but if one of them is damaged or not closed properly, liquids may enter the I/O compartment they protect but they can't get into the interior of the tablet. Doing it this way is more complex, but potential damage is limited to an I/O module and not the entire tablet. And I say "potential" damage, because Dell actually applies what they call HZO liquid protection and describe as a "nanotechnology solution that inoculates electronic components from damage and failure."

An additional advantage of separating I/O modules from the motherboard is that this makes it much easier to upgrade and/or customize I/O. No need to redesign the motherboard.

Even though the internal layout of the Dell Rugged Tablet is complex, components such as WiFi (ours had an Intel Intel Dual Band Wireless AC 8265, Model 8265NGW half-card), PCIe NVMe SSD mass storage, GPS (NEO-M8N), and other wireless modules, as well as the various antenna blocks, are easily accessible once the tablet has been opened.

The modularity, of course, is in Dell's DNA, the result of decades of offering an almost infinite number of permutations of options available right on Dell's website. So almost any feature for which there might be alternatives — or of which a customer might want more or less of — is not on the motherboard but designed as modules.

One thing that's immediately obvious is that the Dell Rugged Extreme Tablet packs industrial-grade thermal management. That includes a fairly sizable fan with a heavy metal enclosure that, of course, is sealed towards the interior of the device. Two copper pipes conduct heat away from the processor, ancillary electronics, and also the PCIe-based SSD.

So that's one major difference to the initial Dell Rugged Tablet that only had a tiny and nearly invisible fan and no heat pipes. Makes sense, as the original tablet's processor had a TDP rating of just 4.5 watt whereas the one in this tablet is a 15 watt design.

But 15 watts is still considered ultra-low voltage by Intel, and aren't all ultra-low voltage processors supposed to be able to operate without fans in Windows tablets?

In the past, yes, under certain circumstances. That's because in the past there was no Intel "turbo" mode, the processor's ability to briefly run at higher (and sometimes much higher) than the nominal clock frequency, as long as temperatures didn't exceed certain levels.

Turbo mode is great, but it can turn into a problem in rugged machines. When a machine gets too hot out there in the desert and there is no active cooling, performance will drop, and can drop to unacceptable levels. That's why Dell chose to use a fan in the 12 Rugged Tablet. This way, performance will not drop, no matter what.

The picture to the right shows the Dell Rugged Extreme Tablet's thermal engineering, taken with our FLIR One Pro infrared camera during a performance test benchmark run.

The bright yellow areas are the hottest, and that is where the heat is conducted away from via the system's copper pipes. On the left side of the tablet you can see the fan, and the plume of hot air ot expels. As a result, even during a sustained high performance load we never saw more than 96 degrees Fahrenheit.

Overall, the interior of the Dell 12 Rugged Extreme Tablet is a complex, sophisticated affair that clearly shows Dell's experience in mobile computing technology. Components and modules are clearly marked and have their own 2D scan code. Wires that go from modules to their respective antennae located around the perimeter of the tablet for best reception are guided and held in place with little loops and guides.

But, regardless of size or sharpness, providing the right display for a system that's being used outdoors is much more difficult than for one that's mostly used indoors in an office or at home. That's because we now have incredibly sharp, photorealistic-grade displays for indoor use, displays that one can't imagine getting much better. But outdoors is a totally different story.

That's because a) it's much brighter outdoors, with even the brightest display not being a match for sunlight, and b) because there are all sorts of reflections that can quickly make a display unreadable.

With regard to LCD outdoor viewability, Dell has been a pioneer. As far back as 2007, Dell had laptop displays that had their screen cover optically bonded to the LCD, thus eliminating the reflections from the LCD surface, eliminating the need to AR-coat the bottom of the screen cover, and eliminating the air gap.

The methods Dell applied reduced overall reflectivity and resulted in a very good effective contrast ratio. At the time, we termed it "definitely readable in sunlight." That was rare back then.

Time doesn't stand still though, and good outdoor-viewable displays are now available from all of the major rugged laptop vendors. Some are offering very high screen brightness of up to 1,500 nits, and optical treatments are continually refined. Dell describes the 12 Rugged Extreme Tablet's "Direct-View" screen as "designed to reduce reflections, preserve contrast and conserve battery life."

In an article entitled "What Really Makes A Mobile Device Screen Readable Outdoors?" Dell Rugged Mobility Marketing Director Patrick Seidensticker reiterated Dell's thought process that led them to concentrate on reducing reflected light as opposed to using battery-draining super-bright backlights. That means reducing the number of layers as each surface reflects sunlight back at the user, or bonding layers together to eliminate surfaces. And it also means using anti-reflective (AR) and anti-glare (AG) coatings. These two measures combined make for impressive outdoor viewability even without a strong backlight.

How well did all this work in the 12 Rugged Extreme Tablet whose display, according to RuggedPCReview's testing, has a maximum luminance of about 560 nits? For illustration, the pictures below are a side-by-side comparison between the 11.6-inch Dell screen and that of an Apple iPad Air 2 we're using around the office for this and that.

Both screens can easily be viewed outdoors, with the Dell tablet somewhat brighter than the iPad, which is said to run at about 450 nits. The iPad's fully glossy display surface, however, reflects far more than the Dell's screen.

Both screens have almost perfect viewing angles horizontally as well as vertically, which is something we consider mandatory in a tablet. There are, however, small differences. While neither tablet loses much brightness when viewed from extreme angles, whites assume a bit of a yellow tinge on the Dell when viewed from extreme angles, whereas color remains unchanged on the iPad.

Today's users are spoiled by the excellent cameras built into smartphones and also by the sophisticated camera imaging apps that are available. The Dell tablet's cameras are not at that level and the Windows Camera app is marginal. The camera are, however, good enough for many documentation tasks, and certainly good enough for decent quality conferencing.

Tough enough for the field