Intel Core i5-661

The Intel Core i5-661 is a dual-core desktop processor from Intel’s Clarkdale generation, built on a 32 nm process with 382 million transistors on an 81 mm² die. It operates at a base clock of 3.33 GHz with a boost clock of 3.60 GHz, and its benchmark results place it near the bottom of the current performance distribution, holding only the 18th percentile among all CPUs tested. The average benchmark score across its tested workloads is 718, a figure that situates it within a tight cluster of older and low-power parts.

Benchmark Performance

The Core i5-661’s benchmark results are modest across all tested workloads. In Cinebench R15 multi-core, it scores 210 points, while in Cinebench R20 multi-core it reaches 876 points. The R20 single-core test yields 123 points, and the R23 versions produce 2088 points multi-core and 294 points single-core. These figures are consistent with a dual-core, four-thread part from the early 2010s, and the data shows that its performance is heavily constrained by its two physical cores.

When compared to its nearest rivals, the i5-661 is essentially tied with each of them, with deltas that are all within one percentage point. Against the Intel Core i3-3250, the i5-661 trails by a negligible 0.1% in average score, with the i3-3250 posting 719 points versus 718 for the i5-661. The Intel Core i7-3667U, a low-voltage mobile part, is 0.3% ahead with 720 points. Conversely, the Intel Core i3-5015U and the AMD Phenom II X4 850 are behind the i5-661 by 0.4% and 0.6%, respectively, with average scores of 715 and 714. These deltas are within run-to-run variance, indicating that the i5-661 delivers performance statistically indistinguishable from these four rivals in aggregate benchmarking.

The 18th percentile ranking reinforces this picture. The i5-661 sits in the bottom fifth of all tested CPUs, which is expected for a part with only two cores and a 3.33 GHz base clock. Its Cinebench R23 multi-core score of 2088 is roughly 2.4 times its single-core score of 294, a ratio that reflects the limited scaling from just two physical cores with Hyper-Threading. The data suggests that this processor is suitable only for basic productivity tasks, not for heavily threaded workloads or modern gaming.

Power and Thermals

The Core i5-661 carries a TDP of 87 watts, which is notably high for a dual-core processor by contemporary standards. This TDP class implies that the chip requires a dedicated cooling solution beyond a basic stock cooler, likely a mid-range air cooler or a low-profile tower cooler to maintain reasonable temperatures under sustained load. The 32 nm process node helps mitigate heat output, but the 87-watt envelope still places it in a tier where thermal headroom is limited, especially in small-form-factor systems.

Given the 87-watt TDP, the i5-661 is not a power-efficient option for modern builds. The data shows that its performance per watt is poor when compared to newer dual-core parts, many of which consume less than half that power while delivering similar or better scores. For a system builder, this means the i5-661 would require a power supply with adequate headroom for the CPU’s draw, but no exotic cooling is necessary — a capable air cooler with a 92mm or 120mm fan would suffice for stock operation. The lack of ECC memory support further aligns this part with consumer desktops rather than workstations or servers.

How It Compares

Intel Core i3-3250: The i3-3250 is the closest competitor, with an average score of 719 versus 718 for the i5-661, a delta of -0.1%. Both are dual-core parts with integrated graphics, but the i3-3250 is from the Ivy Bridge generation, which typically offers better instruction-level efficiency. In practice, the two are interchangeable in benchmark terms, though the i3-3250’s newer architecture may provide slight advantages in memory latency-sensitive workloads.

Intel Core i7-3667U: This mobile chip posts 720 points, a 0.3% lead over the i5-661. The i7-3667U is a low-voltage part designed for ultrabooks, yet it matches the desktop i5-661 in aggregate performance. This underscores the i5-661’s age; a power-constrained mobile processor from the same era can keep pace with it. The i7-3667U’s advantage likely stems from its Turbo Boost capabilities, which allow higher single-core clocks despite a much lower TDP.

Intel Core i3-5015U: The i3-5015U scores 715 points, 0.4% behind the i5-661. This is a Broadwell-era dual-core with a 15-watt TDP, making it far more efficient than the i5-661. The data shows that a modern low-power part can match a desktop chip from 2010, which highlights how far process improvements have shifted the performance-per-watt curve. For battery-powered laptops, the i3-5015U is clearly the superior choice.

AMD Phenom II X4 850: The Phenom II X4 850 has four physical cores and scores 714 points, 0.6% behind the i5-661. This is a notable comparison because the Phenom has twice the core count, yet the i5-661’s higher clock speeds and newer architecture allow it to edge ahead in the average benchmark. The delta is small, but it demonstrates that raw core count is not a guarantee of superior performance when per-core efficiency differs significantly.

FAQ

Q: What is the release date of the Intel Core i5-661?

A: The processor was released on January 6, 2010, and its production status is listed as end-of-life.

Q: What is the TDP of the i5-661, and what cooling does it require?

A: The TDP is 87 watts. This implies the need for a dedicated air cooler; a basic stock cooler may struggle under sustained load, but a capable aftermarket air cooler is sufficient.

Q: How many cores and threads does the i5-661 have?

A: It has 2 physical cores and 4 threads, enabling simultaneous multi-threading for improved parallel workload handling.

Q: What is the launch MSRP of the i5-661?

A: The launch MSRP was $196.

Q: Does the i5-661 support ECC memory?

A: No, ECC memory support is not available on this processor.

Q: How does the i5-661’s average benchmark score compare to the AMD Phenom II X4 850?

A: The i5-661 has an average score of 718, which is 0.6% higher than the Phenom II X4 850’s 714 points.

Single-Thread vs Multi-Thread Behavior

The split between single-thread and multi-thread performance is revealing for this processor. In Cinebench R23, the single-core score is 294, while the multi-core score is 2088. The ratio of multi-core to single-core is approximately 7.1x, which is higher than the theoretical 2x scaling from two cores, because the multi-core test benefits from the four threads and the boost clock of 3.60 GHz. This indicates that the i5-661’s multi-threaded performance scales reasonably well for a dual-core part, but the absolute scores remain low.

In Cinebench R20, the single-core score is 123, and the multi-core score is 876, a ratio of 7.1x as well. This consistency suggests that the processor’s thread scheduling and cache hierarchy are balanced. The 4 MB of shared L3 cache helps mitigate the latency of the dual-core design, but the lack of additional physical cores means that heavily threaded applications, such as video rendering or scientific simulations, will see only modest throughput. For single-threaded workloads like web browsing, office applications, and legacy games, the 3.33 GHz base clock and 3.60 GHz boost clock provide adequate responsiveness, though the 18th percentile ranking places it below most modern processors.

The data indicates that the i5-661 is best suited for single-threaded tasks where its clock speed can shine. Multi-threaded performance, while present, is limited by the dual-core foundation, and the benchmark scores confirm that this processor is not a viable option for modern multi-core-heavy software. The 87-watt TDP for this level of performance is a significant drawback, especially when compared to the Intel Core i3-5015U, which delivers nearly identical scores at a fraction of the power. For a system that primarily runs single-threaded applications, the i5-661 can still function, but its age and low percentile ranking make it a poor choice for any new build.