Toshiba Portege Z20t-B Convertible Review

The adaptors for Gigabit-Ethernet (I218-LM) and WLAN (Wireless-AC 7265) supplied by Intel are high-end network components. Besides Bluetooth 4.0, the Wireless-AC 7265 also supports all current WLAN standards in 2.4 as well as 5 GHz networks (802.11a/b/g/n/ac). Thanks to the 2x2 dual-stream technology, the adaptor can reach theoretical transfer rates of up to 866 Mbps; we managed almost 300 Mbps in a perfect environment with the TP-Link Archer C7 router. Both the range as well as the signal quality also left a good impression in our review.

The Portege is equipped with a WWAN module with 3G and 4G support (Sierra Wireless EM7305) to enable fast Internet connections on the road. After the integration of a corresponding SIM card you can use up- and download speeds of up to 50/100 Mbps in LTE networks.

Even though the 2.0 MP Webcam on the front has a slightly higher resolution compared to many rivals, the picture quality is very disappointing: Blurred colors, strong picture noise and mediocre details mean that the camera should only be used for apps like Skype. The 5.0 MP camera with autofocus on the back is slightly better, but it cannot compete with even an inexpensive smartphone. While you could ignore this – after all, a business tablet is not designed to take holiday pictures– the voice recordings of the corresponding microphone are annoying; you should avoid web conferences without a headset.

The display is based on the higher-quality IPS panel, which has a rich black value (0.39 cd/m²) and therefore a correspondingly high contrast ratio (870:1). That the picture is not quite as brilliant as the Surface Pro 3, for example, is due to the matte screen surface, which however, has other advantages–more on that later.

A look at the colors and the grayscale performance shows that the factory settings for the panel of the Portege are not good. DeltaE 2000 deviations of between 9 and 10 are quite disappointing for a professional device, so we recommend calibration. The grayscale in particular is almost perfect after that, only some blue colors still miss the reference values. Probably, the very limited color space prevents even better results.

The Intel Core M-5Y71 is currently the top version of the very frugal Core-M family. With its TDP of just 4.5 watts, the dual-core chip is much more frugal than common ULV CPUs that are usually specified with a TDP of 15 watts. The processor still manages a respectable 1.2 to 2.9 GHz (Turbo Boost) and supports Hyperthreading, so you can execute up to four threads simultaneously. The SoC includes an HD Graphics 5300 graphics card  as well as a dual-channel memory controller – in this case equipped with an 8 GB LPDDR3-1600 memory.

If you can live with 4 GB of RAM and the slightly slower Core M-5Y51 (1.1 to 2.6 GHz), then you can save around 200 Euros (~$213) with the otherwise identical sibling Portege Z20t-B-103.

A power consumption of just 4.5 watts with a (Turbo) clock of almost 3 GHz – how can that work? The simple answer: It does not. The Core M-5Y71 actually reaches the advertised maximum frequency, but only for very limited periods of load peaks and it exceeds the TDP limitation. The processor starts with the full 2.9 GHz (8.3 watts) in the Single-Thread test of Cinebench R15, but drops to 2.3 GHz (6 watts) after a few seconds. We can see a similar behavior in the Multithread scenario, where the clock starts at 2.6 GHz (12.5 watts) and drops to 1.8 GHz (6 watts). These results suggest that Toshiba has raised the TDP from 4.5 to 6 watts – a simple, but effective method to increase the performance that is also used by other manufacturers.

At least temporarily very high clocks ensure a very fast response and good results in short benchmarks. However, the difference compared to "normal" 15-watt models get bigger the longer the load period lasts. Another problem is that the Portege gets so warm after around 10 minutes of maximum load that the power consumption has to be reduced down to 5 watts (in steps).

Generally, the consumption is throttled to 4.5 watts on battery power and this value is not exceeded even for short periods. The result is a reduced clock of 2.0 GHz (Single-Thread) and 1.5 GHz (Multithread), respectively, which obviously affects the performance.

The storage solution is a 256 GB M.2 SSD from Toshiba (HG6), which is based on Toshiba's own controller as well as 19 nm MLC-NAND. Our benchmarks with AS SSD and CrystalDiskMark determine an excellent performance for the drive, both with sequential as well as 4K transfers – significantly better results are currently managed by only a few (and still very rare) PCIe-SSDs. However, the performance differences between modern SSDs are hardly noticeable in practice anyway, so a business device is more focused on the consumption (0.065 to 2.5 watts) and the reliability (MTTF: 1,500,00 hours).

Although the maximum Turbo Boost cannot be maintained, it can catch load peaks surprisingly well. The TDP or temperature limit, respectively, is hardly a problem with everyday tasks like the loading of a website, application launches or installations that usually only stress the processor for a few seconds; even short idle periods are sufficient to fully utilize the Turbo again. In combination with the responsive SSD you get a very powerful working device – at least if you do not plan to use complex rendering or simulation software. In that case, you would be better off with a 15-watt CPU like in the Surface Pro 3.

The graphics core of the HD Graphics 5300 is basically identical to the HD Graphics 5500, which can be found in several ULV models. Both chips represent the medium evolution of the Broadwell GPU, "GT2", with 24 Execution Units (EUs) each. With 300 to 900 MHz, the clocks of the HD 5300 are just slightly lower than most HD 5500 chips on paper, but the real difference is much bigger because of the different TDPs.

The result is that the HD 5300 is not only beaten by the HD 5500 (represented by the ThinkPad T450s), but also the older HD 4400. Complex 3D applications will not run very well on the Portege, but the GPU is more than sufficient for multimedia purposes, including the playback of 4K H.265 videos.

The drawbacks of the passive cooling solution are apparent when you look at the temperature development. The back of the device gets noticeably warm with everyday tasks and we can measure more than 40 °C (~104 °F) in some spots under load. Unfortunately, the ultimate hotspot is where the user holds the device with the right hand – although the processor runs with a slightly lower clock on battery power (and therefore limits the heat development), it would have been better if Toshiba located the Broadwell chip in the center of the chassis.

The integrated sensors of the Core M-5Y71 determine around 85 °C (~185 °F) at the end of our one-hour stress test, which is also the reason for the lower TDP of just 5 watts. We remember: The CPU can actually consume up to 6 watts, but the temperatures will limit the performance after a while.

It is always surprising how mobile and powerful modern convertibles have become now – a passively cooled Core-M device is hardly slower than a real desktop PC in many daily situations: But: Besides Toshiba, rivals like Lenovo or Dell manage this as well and use the same hardware platform for their devices.

So why should you pay almost 2000 Euros (~$2138) for the Portege Z20t, if you can get a ThinkPad Helix 2 or Venue 11 Pro for a much lower price? We have to be fair and emphasize that the Toshiba comes with many accessories, which have to be purchased separately in the case of the rivals. As well as the two digitizers and the integrated LTE module, we are talking about the keyboard dock with the secondary battery, which enables extremely long battery runtimes. The matte touchscreen of the Portege is another unique characteristic and is extremely helpful outdoors. The quality of the 2-in-1 notebook does not reveal any issues: The build quality is very good and the input devices are suitable for prolific writers.

Overall, the Portege Z20t is an interesting device for wealthy business customers that are looking for a versatile working device with an extremely good mobility. Private users that can dispense with certain features and security solutions will find rivals for a lower price.