Intel Skylake i5-6500, i5-6400 & i3-6100 Review

Author: SKYMTL
Date: February 21, 2016
Product Name: i5-6500, i5-6400 & i3-6100
Part Number: BX80662I56500 / BX80662I56400 / BX80662I36100
Warranty: 3 Years
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When Intel first launched their Skylake processors, buyers’ choices were essentially limited to a pair of options: the i7 6700K and later the i5 6600K. Both boasted features enthusiasts looked for like unlocked multipliers and fast out-of-box performance but they were also priced accordingly. These remained the only two possibilities for Skylake-bound buyers until late last year when Intel finally rolled out a top-to-bottom lineup.

The way Intel has approached Skylake’s cadence into lower price points has been drastically different from previous generations. Instead of offering a broad range of products from day one, additional i5, i3 and Pentium-class CPUs became available in fits and spurts, sometimes months after their initial “launch” dates. Much of this odd rollout seems to have been dictated by challenges brought about by Intel’s advanced 14nm manufacturing process, one which has effectively broken the ground rules set out by Moore’s Law. Simply put, Intel can’t produce Skylake processors fast enough to satisfy the market’s demand.

While this situation could eventually play into AMD’s hands provided their Zen microarchitecture meets expectations, for the time being this isn’t negatively impact Intel’s commanding market share. It has however contributed to prices remaining high which has pushed potential customers to lower price points. Many have asked themselves whether or not those unlocked multipliers that distinguish K-series processors are really worth the investment.

Enthusiasts who really want to push their systems will always gravitate towards overclocking. However, some of these more affordable alternatives could be an excellent option if a user believes the money saved versus something like the i7 6700K would be better invested in a motherboard with a huge feature set or a better graphics card.

This all brings us to the three processors in today’s review, namely the i5-6500, i5-6400 and i3-6100. All of these have been chosen for their price points above all else but there is a notable absence: the i3-6300. Unfortunately, since we purchased all of these processors it was the only one which wasn’t available but, on paper at least, it really doesn’t offer that much more than the i3-6100.

The $192USD i5-6500 is a processor many have considered to be a fitting replacement for the significantly higher priced i5-6600K. It offers Base and Boost frequencies that are within a mere 10% of Intel’s lowest-priced unlocked Skylake CPU while still incorporating four native processor cores, a 6MB cache and a 26W lower TDP. Unfortunately the 3.6GHz max Turbo speed is a far cry away from the 8-threaded i7-6700K’s 4.2GHz but the i5-6500 costs nearly $150 less.

Judging from the response on various online forums, the i5-6400 is considered by many to be the black sheep of Intel’s lineup. While it still includes four native processor cores and a quartet of threads, its base clock (typically what the processor will run at under heavily multithreaded workloads) and graphics clock are much lower than the 6500’s despite a slim $15 cost savings. TDP also remains identical to its more expensive sibling at 65W.

The benefits of a native quad core processor in today’s workloads can’t be overlooked. Hence, regardless of how efficient Intel’s Hyperthreading technology is, a dual core CPU like the i3-6100 which can process up to four threads will typically fall behind its more expensive quad core siblings. Nonetheless, this inexpensive sub-$120 processor can still tackle multi-threaded workloads with aplomb and its “virtual” threads will become transparent to certain applications. There’s also the potential to see performance pushed well ahead of previous-generation Haswell processors since Skylake’s HyperThreading algorithms have been improved.

Past its obvious efficiency advantage there’s a lot to differentiate the i3-6100 from the other processors in this review. It goes about its business without Turbo Boost functionality so instead of dynamically increasing clock speeds when the chip’s TDP allows, 3.7GHz is the constant running frequency. That’s actually quite impressive given the i5-6500 tops out at 3.6GHz. However, while clock speeds seem to be well aligned with higher end alternatives, the i3-6100’s meager 3MB of unified cache will likely hold back performance in some applications.

Added to our i7-6700K, we now have the potential to get a good snapshot of the Skylake lineup at several different price points. While every buyer loves to see how enthusiast level products handle themselves, the reality is that very few actually end up buying those expensive leading-edge wares. Our intent is to see how these less popular family members line up. Many will end up looking towards the i5 and i3 product stacks for their upgrade or new system needs; at the high end (the i5-6600K) they offer unlocked multipliers while something like the i3-6100 could allow someone to maximize the money invested in other components. Honestly, few require overclocking and even fewer games make use of anything more than four threads so any one of these three processors we’re about to cover could be an excellent choice.

Typically our introduction would end here and the benchmarks would start rolling but overclocking does need to be mentioned since it’s recently become something of a hot potato issue. While the locked nature of non-K processors effectively eliminates straightforward overclocking by simply increasing the multiplier, motherboard manufacturers had begun rolling out BIOSes which allowed Base Clock (BCLK) increases. This was significant since the CPU’s running frequency is derived from the base clock (typically 100MHz) and multiplier so with the latter being locked down, higher clock speeds could be realized by manually increasing the BCLK.

With Skylake’s BCLK infinitely more tractable than previous generations, budget-minded overclockers could suddenly buy a less expensive processor that could be overclocked to a point where it competed against much more expensive K-series chips. For example, we saw i5-6400’s easily reaching 4.1GHz with a Base Clock of 125MHz. Actually achieving those overclocks was more challenging than multiplier-based overclocking but it was still possible…..until last week.

We won’t delve into all the speculation surrounding this but for whatever reason, the non-K overclocking BIOSes which motherboard manufacturers were so quick to market suddenly started disappearing. All of them are still available on archive sites but key microcode and platform fixes which were rolled out in the last few weeks aren’t included on those earlier files. They’re essentially a dead end and no longer even supported by the manufacturers who originally released them.

Taking this into account, we’ve actually cut out overclocking from this review but the lack of any possible performance boost through higher than reference frequencies shouldn't dissuade you in any way. All of these CPUs offer some pretty impressive results straight out of the box.

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