i5-6600K vs. i7-6700K for Gaming: Used Market Review

The Short Answer: Hyper-Threading Makes or Breaks Skylake

Buying a used Skylake processor today comes down to a single spec: Hyper-Threading. The four-core, four-thread Core i5-6600K regularly chokes on modern frame times, while the eight-thread Core i7-6700K can still hold a steady 60 FPS in lighter competitive titles and older backlogs.

Neither chip belongs in a brand-new PC build. But if you already own an LGA1151 motherboard (Z170, H110, B150, or Z270) and want a cheap drop-in upgrade from a dual-core Pentium or Core i3, here is how the two stack up.

• Best Drop-In Upgrade: Intel Core i7-6700K (around $45 used) — 8 threads keep frame pacing stable in esports and older AAA games.
• Budget Minimum: Intel Core i5-6600K (around $25 used) — Fine for pre-2018 games and indie titles, but stutters badly on modern game engines.
• Smarter Modern Pick: Intel Core i3-12100F ($75 new) — Outperforms both chips across the board while running on modern LGA1700 motherboards with PCIe 4.0/5.0 support.

Core Specs: Skylake Head-to-Head

Both CPUs were launched on Intel's 14nm process in late 2015. They share the same LGA1151 socket, support DDR4 (and DDR3L) memory, and feature an unlocked multiplier for overclocking on Z-series chipsets. The architectural separation is strictly clock speeds, cache size, and thread count.

Gaming Benchmarks: Why 4 Threads Stutter

Back in 2015, conventional wisdom suggested the i5 was plenty for gaming because titles rarely scaled past four physical threads. That logic has not held up. Modern game engines treat quad-core, four-thread chips as a strict bottleneck.

Pairing these chips with a budget GPU like the GTX 1660 Super or Radeon RX 6600 shows clear daylight between them:

• Counter-Strike 2 & Valorant (1080p, Low/Medium): The i7-6700K averages around 140–160 FPS with steady 1% lows. The i5-6600K averages 110–125 FPS, but dips under 50 FPS during heavy smoke grenades and firefights because background OS tasks fight for the same four threads.
• Grand Theft Auto V (1080p, Very High): Both chips handle GTA V comfortably. The i7-6700K sits near 90 FPS, while the i5-6600K stays around 75 FPS.
• Cyberpunk 2077 (1080p, Low): This is worst-case territory. The i5-6600K sits pegged at 100% CPU utilization across all four cores, resulting in massive audio dropouts and severe hitching (1% lows under 20 FPS). The i7-6700K, thanks to Hyper-Threading, maintains a playable 40–48 FPS average.
• Apex Legends (1080p, Competitive Settings): The i7-6700K stays comfortably above 75 FPS. The i5-6600K regularly experiences micro-stutters when dropping into hot zones.

The issue on the i5-6600K is not always the average frame rate; it is the frame time consistency. When a four-thread CPU hits 100% load, inputs feel sluggish and the screen micro-freezes. The extra four logical threads on the i7-6700K soak up background Windows processes, Discord voice chat, and game physics without grinding to a halt.

Overclocking and Platform Quirks

Both processors overclock relatively well if you have a Z170 or Z270 board and a decent tower cooler. Most i5-6600K chips can hit 4.4 GHz to 4.5 GHz with a moderate voltage bump (around 1.30V–1.35V). The i7-6700K usually reaches 4.5 GHz to 4.6 GHz with similar effort.

Overclocking the i5-6600K boosts its average frame rates, but it does not fix the fundamental thread-starvation issue in newer engines. A 4.5 GHz i5-6600K still loses to a stock i7-6700K in frame time stability.

Editorial note: Skylake chips used thermal paste under the integrated heat spreader (IHS) rather than solder. After a decade, that stock paste has often dried out. If you buy a used 6700K that runs unusually hot under a 120mm tower cooler, delidding and applying fresh thermal compound or liquid metal is the best fix.

Used Market Value: What Should You Pay?

Do not overpay for old Silicon. On platforms like eBay, sellers often ask $70 or more for an i7-6700K simply because it was once a flagship. That is terrible value.

• Core i5-6600K: Worth it only if you can find it for $20 to $25. It makes a decent brain for an ultra-cheap emulation box, a home NAS, or a secondary PC for lightweight indie games.
• Core i7-6700K: Reasonable at $40 to $50. Anything above $55 is wasted money because you are approaching the cost of modern budget platforms.

Buying New Instead?

If you are planning a system build from scratch, do not buy either of these CPUs or their motherboards. Old platforms lack official Windows 11 support, lack PCIe 4.0, and carry dead-end upgrade paths.

For roughly $150 to $170 total, you can buy an Intel Core i3-12100F (or AMD Ryzen 5 3600) paired with an entry-level H610 or B450 motherboard. A 12th-gen Core i3 features four cores and eight threads with architectural IPC gains that crush an overclocked i7-6700K by more than 40% in single-threaded performance while consuming less power.

FAQ

Does the i5-6600K or i7-6700K officially support Windows 11?

No. Microsoft officially requires 8th-generation Intel Core processors (Coffee Lake) or newer for Windows 11. While you can bypass the requirements with registry modifications or tools like Rufus, these chips are officially capped at Windows 10.

Can I put an i7-6700K on an H110 or B150 motherboard?

Yes. The i7-6700K works on any 100-series or 200-series motherboard (H110, B150, H170, Z170, B250, H270, Z270). However, non-Z motherboards will prevent CPU overclocking and will lock your RAM speed to the platform maximum (2133 MHz on 100-series, 2400 MHz on 200-series).

Is the i7-7700K a better purchase than the i7-6700K?

The i7-7700K (Kaby Lake) is essentially an identical chip clocked roughly 200–300 MHz higher out of the box with slightly better hardware video decoding. Performance is within 5% to 8% of the i7-6700K. Buy whichever one is cheaper on the used market; neither is worth a substantial price premium over the other.