If we're talking about idle power, it is mostly that the power management hasn't been tuned for power saving as much as for stable performance, and that there is more power-hungry hardware in the system. The presence of a discrete GPU rather than the typical iGPU. A chipset with more external controllers, most of which may not be properly powered down at idle. Often more than one storage device. And finally, a RAM configuration that is also more power hungry at idle due to the type and quantity of chips, and the high-performance configuration.
I have a Xeon E5-1650v3 6-core workstation in my office with 64GB of RAM, two 7200 RPM disks running constantly, two SATA SSDs, and a GeForce GTX Titan X GPU. According to UPS self-reporting, it is drawing ~80W when essentially idle. The powertop utility reports ~90% C6 idle state for the CPU cores and ~55% C6 idle state for the package.
I have an i3-8100 4-core PC at home with 16GB of RAM, two 5400 RPM disks which are set to spin down, one nvme SSD, and the iGPU. According to UPS self-reporting, it is drawing under 15W. The powertop utility reports ~97% C7 idle state for the CPU, ~99% RC6 for the iGPU, and doesn't report a package idle state.
I have an older i7-4700MQ 4-core Thinkpad with 16GB of RAM, one SATA SSD, and a discrete GeForce GT 730M GPU alongside the iGPU. It is drawing about 13W off the battery with screen active but at low brightness so I can query it locally and write this post. The powertop utility reports ~95% C7 idle state for the CPU, ~99% RC6 for the iGPU, and ~60% C2 plus ~23% C3 for the package.
Old Xeon CPUs, especially dual socket ones, just tend to be the highest TDP ones. The Xeon E5-2667 v2 mentioned in the article is a 130W CPU, which he compares to the AMD Ryzen 7 2700X which is 105W. The AMD, in benchmarks is around 5% faster.
I was honestly expecting more of a different there in both speed of the AMD and power consumption of the Xeon. If you get a workstation with two of them, you're talking about 260W max consumption. And of course that is max consumption, idle consumption is probably more important and is probably way, way lower.
One place where some of these machines really shine though is in memory availability. If you need a lot of RAM, it can be hard to get a new desktop that'll take more than 64GB, but workstation chipsets can often go to half a TB or more. Of course, that RAM uses a lot of power...
I have a E5-2670 (V1) based system and the idle power draw is around 80W. I doubt a modern system with the same cores and threads (say an i9-9900k) is going to draw that much less while idle. Even if it uses half the power, that equates to electricity savings of under $5 per month if it's on 24/7.
Back in those days, Intel simply did not care one iota about power consumption. The P4 processors were absolute power hogs, and all Intel did was brag about how great their memory bandwidth to the RAMBUS memory was.
The last Pentium 4 was released in 2008; the Xeon E5-2667 v2 parts discussed in the article were released in 2013, years after Intel abandoned their Netburst approach.
