Pros: Fast, 6 core/12 threads, 40 PCIe lanes, quad memory, excellent IOMMU group separation/ACS, overclocking
Cons: Price, power consumption, heat, only 2*6GB/s SATA ports
1. Good virtualization and IOMMU support (VT-d in Intel terminology);
2. Life expectancy.
Background: I was building a new rig that would run Linux as the host operating system and Windows as a virtual machine. The Windows VM has its own graphics card, which is passed through to the VM using a technology called VGA passthrough. The Windows virtual machine then runs practically at the same speed as when installed directly onto the hardware.
The 3930K processor offers a feature called IOMMU (VT-d). This is a must for doing VGA passthrough. Compared to Intels consumer type CPUs the 3930K has much more in common with the Xeon series of server CPUs, including excellent IOMMU support. Today (5 years later) many Intel CPUs are listed as supporting VT-d/IOMMU, but that itself doesn't mean much. The actual feature behind IOMMU is ACS or Access Control Services that separate different PCIe devices into separate IOMMU groups.
The 3930K cleanly separates different PCIe slots and devices into different IOMMU groups, whereas some of the consumer type CPUs that also support VT-d/IOMMU put different devices into the same group. There are workarounds (ACS patch in Linux) but no workaround can fix a sloppy design.
Another welcome feature in the 3930K is 40 PCIe lanes. The CPU comes without GPU which means that in my configuration I need 2 graphics cards to support Linux and Windows simultaneously. I also use a discrete Asus Xonar Essence PCIe sound card, and a PCIe SATA / USB3 controller board to support all the disks I've installed. In other words, my rig makes full use of the 40 lanes.
I use Linux for everyday tasks (email, web browsing, web design, etc.) and Windows 10 for photo editing in Lightroom and some other Windows/Mac-only applications. 5 years ago I had a 12MP camera, today I'm using 3 cameras with 12MP, 16MP, and 24MP. My next camera will likely have 36-40MP. I'm shooting RAW and all files have to be converted to jpg and/or tiff. What I'm saying is that today, 5 years later, the RAW files have increased to about double the size. Editing and conversion of these larger files takes more resources. Yet, the 3930K is still going strong!
In the past I would have to upgrade my computer hardware/CPU every 3 years, just to ensure a decent workflow speed when processing photos. With the 3930K CPU, I'm essentially running the same rig I built 5 years ago, except GPU and SSD upgrades/additions. The PC is keeping up with the higher demands from larger RAW files. Not only that, my workflow has changed and I'm using more editing steps and external software to create the look I want. This requires even more processing power.
So far I have been writing about my experiences under Windows. But my host OS is Linux. There the 6 core CPU really shines! Linux and Linux-based software is so much better in utilizing multiple cores. Running a backup of my Windows VM partition to a gzipped file using pigz for parallel compression crunches through 110GB in about 10 minutes - the speed being limited by my HDD drives speed. I converted my collection of ~1,500 music CDs to flac, using two CD/DVD drives to keep up with the speed. Ripping my DVD collection using handbrake was a breeze.
It is rather sad that commercial software such as Adobe Lightroom and Photoshop, both under Windows, still cannot make good use of multiple cores (see Adobe Lightroom CC/6 Multi Core Performance). Whether this is the result of sloppy programming or company policy having priorities elsewhere, I can't tell. It is certainly not the fault of the CPU.
That said I'm actually hopeful in that future releases of these applications and other commercial software will improve multitasking and parallel processing capabilities. If and when that happens, this little old 3930K CPU may actually become better with age compared to recent 4 core brethren.
Will a newer CPU speed up my photo editing workflow? Depending on which CPU, yes. But the 3930K is still holding its turf against most of the newcomers. If I was to buy a CPU now, which one(s) would I consider:
1. i7-7820X - same price range as my current 3930K, but 8 core and higher clock speed on a X299 board;
2. i7-7740X - lower cost, lower performance, with 4 cores only on a X299 board - upgradable to the 7820X;
3. i7-7700K - same cost as 7740X, but cheaper motherboard options (Z170, Z270, for example)
Owning a 3930K CPU, the only way to significantly improve performance would be the i7-7820X. Since the 3930K has plenty of resources to process 24 MP RAW photos I can wait perhaps another 2-3 years before this build becomes obsolete and I need to upgrade.
5 years on the same CPU is an achievement, considering that I use it for image editing. I am hopeful that I can use this CPU/board for another 2-3 years. When comparing the 3930K with the choices at the time (i7-2600, i7-3770, both non-K since their "K" versions do not support VT-d), it's obvious that the other options would have been obsolete by now. The 3930K has been a good investment, and with each more year the investment becomes an even better one.
So far I didn't have the need for overclocking. But user reports show that it can be overclocked from 3.2 to at least 4.0, with 4.5GHz and more being the standard. That translates into a 25-30% performance gain which would significantly narrow the gap between the 3930K and current CPUs.
To sum it up: The i7-3930K 6 core CPU was/is a powerful CPU offering excellent multithread performance and rock-solid virtualization capabilities. With that much performance and the option for serious overclocking, this CPU still runs strong after 5 years and 5 new generations of CPUs. This is awesome .
The only reason I'm not giving it a 5-star rating is for the high power consumption and the heat it produces. It requires a good cooling system.