Intel Core i7-1355U vs Intel Core i7-8700K Comparison

Head-to-Head Benchmarks

The benchmark data between the Intel Core i7-8700K and the Intel Core i7-1355U shows a clear split: the newer mobile chip dominates in raw frequency-sensitive tasks, while the older desktop part retains advantages in sustained throughput and legacy instruction workloads. Out of 17 recorded benchmarks, the i7-1355U wins 13, with the i7-8700K taking only 4.

The most dramatic single-core result comes from Cinebench R15 single-core, where the i7-1355U scores 255.5 against the i7-8700K's 163, a 36.2% advantage. This gap narrows in Cinebench R20 single-core (698 vs 683, a 2.1% lead for the mobile chip) but expands again in Cinebench R23 single-core, where the i7-1355U's 1825 beats the i7-8700K's 1627 by 10.8%. PassMark single-thread tests echo this trend: 3444 vs 2720, a 21% lead for the i7-1355U.

Multi-core results are more nuanced. In Cinebench R15 multi-core, the i7-1355U leads 1393 to 1161 (16.7% ahead). In Cinebench R20 multi-core, the margin shrinks to just 2.2% (4949 vs 4841). But Cinebench R23 multi-core flips the script entirely: the i7-8700K scores 11527 versus 8286, a commanding 39.1% advantage. This suggests the older chip sustains higher performance over longer render workloads, while the mobile CPU's advantage fades under extended load.

PassMark tests show a mixed bag. The i7-1355U wins floating point math (34965 vs 28538, 18.4% ahead), integer math (52002 vs 45892, 11.7% ahead), and physics (888 vs 811, 8.7% ahead). It also wins multithreaded performance (14299 vs 13576, 5.1% ahead) and prime number finding (51 vs 39, 23.5% ahead). The i7-8700K counters with major wins in data compression (198951 vs 155727, 27.8% ahead), extended instructions (13514 vs 8726, 54.9% ahead), and random string sorting (25270 vs 17631, 43.3% ahead). Data encryption heavily favors the i7-1355U: 9831 vs 4776, a 51.4% gap.

Overall average benchmark scores sit close: the i7-8700K averages 19238, while the i7-1355U averages 18730. Both sit at the 73rd percentile among all CPUs. The i7-8700K's nearest rivals include the Intel Core i7-10700 (0.5% ahead), AMD Ryzen 5 7533HS (0.6% behind), Intel Core Ultra 5 226V (0.7% behind), and Intel Core i5-1345U (0.9% behind). The i7-1355U's nearest rivals include the AMD EPYC 7643 (0.2% ahead), Intel Core i5-12400 (0.3% ahead), AMD Ryzen AI 5 330 (0.4% behind), and Intel Core i3-14100F (1.1% ahead).

FAQ

Q: Which CPU is faster in single-core workloads?

A: The Intel Core i7-1355U wins every single-core benchmark recorded. It leads by 36.2% in Cinebench R15, 2.1% in Cinebench R20, 10.8% in Cinebench R23, and 21% in PassMark single-thread tests.

Q: Does the older i7-8700K beat the mobile chip in any multi-core test?

A: Yes, specifically in Cinebench R23 multi-core, where the i7-8700K scores 11527 versus 8286, a 39.1% advantage. However, the i7-1355U wins Cinebench R15 multi-core (1393 vs 1161) and Cinebench R20 multi-core (4949 vs 4841).

Q: How do their overall average scores compare?

A: The i7-8700K has a slightly higher average benchmark score of 19238, compared to the i7-1355U's 18730. Both sit at the 73rd percentile among all CPUs.

Q: Which CPU handles encryption workloads better?

A: The i7-1355U is dramatically better, scoring 9831 in PassMark data encryption versus the i7-8700K's 4776, a 51.4% advantage.

Q: What about legacy or specialized instruction performance?

A: The i7-8700K excels here. It leads PassMark extended instructions by 54.9% (13514 vs 8726) and data compression by 27.8% (198951 vs 155727).

Q: Does the i7-1355U's lower power consumption affect its benchmark results?

A: The data shows the i7-1355U wins most benchmarks despite its 15W TDP, but the i7-8700K's 95W TDP allows it to pull ahead in longer multi-core renders like Cinebench R23.

Where Each One Wins

The Intel Core i7-1355U is the clear choice for single-threaded applications and short-duration multi-core bursts. Its 5.00 GHz boost clock and newer architecture drive wins in all single-core tests, plus wins in floating point math, integer math, physics, and multithreaded PassMark scores. For everyday desktop tasks, office work, web browsing, and lightly threaded productivity, the i7-1355U delivers noticeably better responsiveness. Data encryption workloads also strongly favor the mobile chip, with its 51.4% advantage making it the better pick for security-related tasks.

The Intel Core i7-8700K wins where sustained throughput and specific legacy workloads matter. Its 39.1% lead in Cinebench R23 multi-core indicates superior long-form rendering performance. The 54.9% advantage in extended instructions and 43.3% lead in random string sorting suggest the desktop chip handles specialized instruction sets and data manipulation tasks more efficiently. Data compression also favors the i7-8700K by 27.8%. For users running heavy multi-threaded renders, compression workflows, or applications that rely on older x86 instruction extensions, the i7-8700K's 6 cores and 12 threads provide more consistent output.

Specification Differences

The two CPUs differ fundamentally in platform, power, and expansion. The i7-8700K uses Intel Socket 1151, while the i7-1355U uses Intel BGA 1744. The desktop chip has a 95W TDP; the mobile chip draws only 15W. The i7-8700K supports DDR4 memory with dual-channel bus and 42.7 GB/s bandwidth. The i7-1355U supports both DDR4 and DDR5, also dual-channel, though its bandwidth is not recorded. PCIe differs: the i7-8700K provides Gen 3 with 16 lanes (CPU only), while the i7-1355U offers Gen 4 with 8 lanes (CPU only). The i7-8700K has an unlocked multiplier; the i7-1355U is locked. Their production statuses differ: the i7-8700K is end-of-life, while the i7-1355U is active. Release dates are October 2017 for the desktop chip and January 2023 for the mobile chip. Launch MSRP for the i7-8700K is $359; for the i7-1355U it is $469.

Architecture Differences

The architectural gap spans two major Intel designs. The i7-8700K uses Coffee Lake on a 14 nm process with a 154 mm² die. It packs 6 cores and 12 threads, with base clock 3.70 GHz and boost 4.70 GHz. Cache is organized as 64 KB L1 per core, 256 KB L2 per core, and 12 MB shared L3. Its integrated graphics are UHD Graphics 630.

The i7-1355U uses Raptor Lake-U on a 10 nm process. It has 10 cores and 12 threads, with a recorded base clock of 1700.00 MHz and boost of 5.00 GHz. Cache differs significantly: 80 KB L1 per core, 1.25 MB L2 per core, and 12 MB shared L3. The integrated graphics are Iris Xe Graphics 96EU. The mobile chip's die size is not recorded in the database.

These architectural differences explain the benchmark splits. The i7-1355U's smaller 10 nm process and higher boost clock enable superior single-thread performance. The i7-8700K's older 14 nm node and larger die produce more heat, but its 6 full-size cores with larger per-core L2 cache (256 KB vs 1.25 MB per core for the mobile chip, note the mobile chip's larger L2 per core) sustain heavier multi-core loads. The i7-1355U's hybrid architecture with 10 cores handles parallel short bursts well, but thermal limits appear in extended Cinebench R23 rendering.

The Verdict

Choose the Intel Core i7-1355U for modern single-threaded performance, lower power consumption, and encryption-heavy workloads. It wins 13 of 17 benchmarks, including all single-core tests and most PassMark integer and floating point tests. Its 5.00 GHz boost clock and Gen 4 PCIe make it suitable for current laptops and compact systems where efficiency matters. The 15W TDP allows for fanless or low-noise designs, and the Iris Xe Graphics 96EU provides more capable integrated graphics than the older UHD Graphics 630.

Choose the Intel Core i7-8700K for sustained multi-core rendering, legacy instruction workloads, and data compression. Its 39.1% lead in Cinebench R23 multi-core shows it handles long render jobs better. The 54.9% advantage in extended instructions and 27.8% lead in data compression make it the better tool for specialized compute tasks. The unlocked multiplier and 16 PCIe Gen 3 lanes suit desktop builders who want overclocking headroom and expandability. The i7-8700K's end-of-life status means it is a legacy pick, but for users with existing Socket 1151 platforms, it remains competitive in specific workloads.

The data ultimately shows two different design philosophies. The i7-1355U maximizes speed per watt, winning most benchmarks while consuming 80W less. The i7-8700K trades efficiency for sustained power, delivering wins where workloads extend beyond short bursts. Neither CPU dominates completely; the choice depends on whether your work favors quick single-threaded responses or long, heavy multi-threaded computation.