The Intel Core i3-7350K (60W) Review: Almost a Core i7-2600K

Core i3-7350K vs Core i7-2600K

When I started testing for this review, finding out how close the Core i3-7350K was to the favored Core i7-2600K was anticipated to be interesting. Several years of IPC increases in favor of the Core i3, plus the extra frequency and overclockability, were to be put against brute force in the form of more, but older, cores. The Core i7-2600K is certainly no slouch. It's a good overclocking chip in its own right, hitting almost 5.0 GHz on a good sample, which has made it a very difficult processor for Intel to get users to upgrade from in this recent area of minimal IPC increases per generation.

That’s not to say that IPC increases are entirely Intel’s fault – at some point there is only so many knobs you can turn and twist in a given CPU microarchitecture. But the lack of IPC gain can come from the big questions: if we have GPUs at 250-300W, why not CPUs? Is Intel’s process focused on performance, power, or die size? If you speak to a few analysts, you get a wide variety of reasoning as to how Intel does things, but money is usually the key factor. This is perhaps a topic to discuss on a podcast!

But to the matter at hand: there will be a time where a Core i3 based CPU will match the performance of the older Core i7-2600K. This is what the testing was about: at what point will we have enough frequency and IPC gain to match the older chip, potentially saving a bunch of power in the process? It’s not necessarily a question of upgrading – high-performance enthusiasts rarely upgrade to a system that gives equal performance at lower power, but it does offer that understanding that perhaps the Core i7-2600K might be showing its age.

At a high level, the two CPUs have the following:

The Core i7-2600K has more cores and more cache. The Core i3-7350K has a higher frequency, better memory controller, better integrated graphics, is more efficient, and was released at almost half the cost. The big question is if frequency plus IPC can match the brute force of more cores.

Throughout the results, each benchmark that has results between the two processors has commentary on the Kaby Lake-i3 vs Sandy Bridge-i7 performance.  Here’s a brief summary:

As expected, the Core i3-7350K takes the single threaded performance win.  In every benchmark the Core i3 was ahead up to +44%, with an average of +25%.

With the multithreaded CPU tests, the extra cores and threads of the older Core i7-2600K were often more than enough to overcome the newer part. The Core i3-7350K does, on average, -18% less work than the Core i7-2600K, which manifests itself as anything from being near equal to a -40% loss in throughput (or taking almost 1.8x the time to finish the same task). Benchmarks that fall into the latter category are mostly tasks that have large threads competing for size in the cache, meaning the contest essentially becomes two cores vs four cores. Even with CPU and IPC, that’s a tough mark to jump over.

For the gaming tests, putting aside the obvious win on integrated graphics for Kaby Lake, in our game tests we saw parity at the high end. Only one serious high-end GPU test saw a win for Kaby Lake, giving +16% performance gain, but the interesting results occur on mid-range cards. For mid-range, the newer Core i3 test out-performed the older Core i7 by an average of 10%, which ranged anywhere from equal to +24% (Mordor at 1080p Ultra).

Ultimately the Core i3 parts are marketed towards the mid-range GPU gaming community, and the addition of overclocking may be enough to push a user to get a Core i3-K instead of a Core i5, migrating money over to a different part of the PC. But for our gaming tests, the Core i3-7350K certainly matches the Core i7-2600K.

Ultimately, however, the users who fully stretch the legs of the Core i7 through other means, such as compute-heavy work, already need the power of all the cores. As shown in our multithreaded tests, while the Core i3 is hot on the heels of the Core i7-2600K, the deficit of having two fewer cores is very difficult to overcome. That becomes more difficult as we overclock both CPUs into the 4.8 GHz region, where the 400-600 MHz frequency advantage of the Core i3 is lost and the contest is purely on IPC, cores and stability.

The Core i3-7350K, as a CPU, is not enough to encourage users who already push the Core i7-2600K to the absolute limit and want to stay there. For everyone else though, where responsiveness is more important, or in casual gaming, the Core i3-7350K becomes an adequate side step from the i7-2600K to decrease power consumption and move onto a new platform (and have the joy of building a new PC again). Windows 10 users also get the benefit of Speed Shift, affording more ‘free’ performance for responsive tasks.

It is worth noting that moving to the Core i3-7350K affords non-CPU related benefits. Moving from a P67/Z68 motherboard to a Z270 motherboard means:

• GPU slots operate at PCIe 3.0, rather than PCIe 2.0 (on Z68)
• More chipset PCIe lanes (24 lanes at PCIe 3.0 rather than 8 lanes at PCIe 2.0)
• Support for bootable NVMe storage and PCIe storage
• Newer audio codecs and networking controllers
• Updated Intel RST (RAID/Caching)
• A move from DDR3-1333 to DDR4-2400
• Native USB 3.0 Ports from the chipset rather than from controllers
• USB 3.1 (10 Gbps) on board via controllers rather than a add-in PCIe card
• Potential Thunderbolt 3 support (depending on motherboard)
• USB Type-C
• This RGB fad that apparently sells like hot cakes
• More SATA 6 Gbps ports (six on Z270 vs two on Z68)

At What Point Will the Performance of A Core i3 Beat the Core i7-2600K?

If we’re only speaking performance (I’m sure Intel would rather happily speak efficiency), judging by our benchmark results, we’re almost there already. For all but the most strenuous tasks that require large caches, the Core i3 already wins out. Unfortunately these are the tasks where the Core i3 needs a clear 2x performance gain per core to match the Core i7-2600K. For these tasks, anywhere from -30% to -40% loss to the Core i3 in our test can be a deciding factor in purchasing.

Let’s take a score based test, such as POV-Ray. Here the Core i3-7350K scored 1009 points, compared to the Core i7-2600K which scored 1323 points (or +31.1%). Based on the overclocking tests, each 100 MHz on the Core i3 resulted in +25 points, and that rise was essentially linear from 4.0 GHz to 4.8 GHz.

With extrapolation, the 314 point deficit requires an extra ~1250 MHz for the Core i3 to match that result.

So, all we need is a 5.45 GHz dual-core processor with Kaby Lake IPC.

Or, think of it another way. If we assume Intel creates a 5% IPC increase year-on-year, a 4.2 GHz Core i3 will score 1059 next generation, then 1112, then 1168, and so on, until we hit a score of 1352 in six more generations. Roll on 2025?

(As an aside, the best tested Kaby Lake CPUs from the world’s best overclockers can reach a semi-stable 5.3-5.4 GHz using water cooling, using AVX offset, but beyond that (and for 100% stability) requires sub-zero cooling.)