The key improvement to the HP Spectre x360 is the upgrade to new 8th gen Kaby Lake Refresh CPUs. What you gain is pretty significant: a shift from two cores and four threads, to four cores and eight threads. This is the first time in a long while that Intel is giving ultraportables more than a 10% performance boost generation on generation.

While you can get Spectre x360 models with both Core i5 and Core i7 CPUs inside, my review unit was loaded with the Core i7-8550U, a highly popular CPU in modern ultraportables, and 16GB of RAM. Its four cores have a base clock of 1.8 GHz and boost between 3.7 and 4.0 GHz depending on how many cores are utilized. Like previous 7th gen parts, it's a 15W CPU built on a 14nm process. It also has UHD 620 graphics with 24 execution units clocked up to 1150 MHz.

It's not a new feature, but one of the key aspects to Kaby Lake-R is its configurable TDP, so while the chips are generally rated for 15W, OEMs can choose a TDP between 10 and 25W depending on their power and cooling subsystems.

If you saw my Dell XPS 13 review a couple of months back, that's a laptop that uses the maximum 25W TDP when connected to the charger for maximum performance.

The Spectre x360 isn't one of those systems. It uses the stock 15W TDP, and even then, it struggles under the power of the Core i7-8550U. It doesn't run loud - the cooler isn't super quiet but it doesn't land a small passenger jet on your desk either - but it does run hot.

During the initial burst of a workload where the CPU hits its peak clock speed, the 8550U quickly hits around 100C and dials back to its low sustained clock very quickly; much quicker than other Kaby Lake Refresh laptops I've tested.

When combined with the use of the stock 15W TDP, the Spectre x360 suffers in both short and long workloads. In Cinebench, for example, the Spectre is 20 percent slower than the Dell XPS 13 in the multi-threaded workload; and six percent behind the more modest Inspiron 13 7000 2-in-1. All three of these laptops use the same CPU but with different coolers and capabilities.

These results are carried over into many other tests. When encoding x264 videos, the Spectre x360 is 22 percent slower than the XPS 13, and 15 percent behind the Inspiron. In Handbrake encoding x265 videos, we're looking at similar performance deficits, and this carried over into Blender as well.

In shorter workloads like Excel, the Spectre x360 ended up 4 percent behind the XPS 13 and 13 percent behind the Inspiron. In MATLAB we're looking at 2 and 12 percent deficits compared to the XPS and Inspiron laptops respectively. Even in WinRAR, the only test where the Spectre x360 got close to the XPS 13, it was still soundly beaten by the quick and high firing Inspiron.

In the more all-round tests of PCMark, it's still not great news for the Spectre x360, falling 5 percent behind in the Home and Work tests while performing around the same mark in Creative, compared to the XPS 13. The Inspiron laptop outperformed HP's offering in all three tests, and in PCMark 10 as well, which didn't work on the XPS 13 for whatever reason.

Similar margins are carried into 3DMark as well, so unfortunately it seems every aspect of the Core i7-8550U's performance has been hampered by the cooling solution compared to the Dell XPS 13, one of the Spectre x360's main laptop competitors.

Of course it's not all bad news for the new Spectre x360. Compared to the previous model, which used a Core i7-7500U, we are seeing significant gains in a number of tests: it's 57 percent faster in Cinebench, 40 percent faster in x264 encodes, 14 percent faster in MATLAB, 20 percent faster in the CPU-limited Cloud Gate 3DMark test, and much faster in compression and decompression.

The main thing to note here is that anyone upgrading from a 7th-gen or older system will see pretty huge gains in CPU performance moving to the 8th-gen Spectre x360. However, this system could have achieved better gains had the cooler been up to the task, as it's soundly beaten by the otherwise similar Dell XPS 13 with the very same i7-8550U.

On the other hand, storage performance is excellent from the Samsung PM961 512GB SSD in my review unit. This drive has great sequential performance and delivers very solid random speeds, putting it in the upper echelon of laptop drives. It does cost a pretty penny for the higher-capacity Spectre x360 models but at least HP is giving you ultra fast storage for the price.