Intel Core i7-3820 vs Intel Core i7-3840QM Comparison

The Intel Core i7-3820 and Intel Core i7-3840QM are two quad-core processors from Intel’s Sandy Bridge-E and Ivy Bridge families, respectively, but they target completely different computing environments. The 3820 is a desktop part with a 130W TDP, while the 3840QM is a mobile chip with a 45W TDP. Despite these fundamental differences in platform and power envelope, the benchmark data shows an exceptionally tight performance race, with the 3840QM winning all six head-to-head Cinebench tests by very narrow margins, ranging from -0.4% to -1.4% deltaPct. The average benchmark scores are nearly identical, with the 3820 at 1424 and the 3840QM at 1416, placing both in the 37th percentile of all CPUs. This creates a curious situation where the higher-TDP desktop processor cannot outrun the more efficient mobile part in the measured workloads, making the choice between them depend almost entirely on platform requirements rather than raw compute capability.

The Verdict

For a desktop user with a Socket 2011 motherboard, the Intel Core i7-3820 is the only option in this comparison, as the 3840QM uses the incompatible Intel BGA 1224 socket. The data shows the 3820 holds its own with a Cinebench R23 multi-core score of 4923, and its unlocked multiplier offers overclocking headroom — a feature the 3840QM lacks. However, anyone building a system from scratch should note that the 3840QM delivers essentially identical performance: it wins the R23 multi-core test with 4952 points, a 0.6% advantage, while doing so at a dramatically lower 45W TDP compared to 130W.

The 3840QM is the better choice for mobile users, as it integrates Intel HD 4000 graphics, which the 3820 lacks entirely, and its 22nm process node with 1,400 million transistors in a 160 mm² die suggests superior efficiency. The 3820’s advantages are platform-specific: quad-channel memory support providing 51.2 GB/s bandwidth versus dual-channel on the 3840QM, and 40 PCIe Gen 2 lanes from the CPU. For pure compute, the verdict is clear from the data: neither chip dominates, but the 3840QM edges ahead in every single benchmark, making it the performance winner despite being a mobile part. The 3820 only makes sense if you need the desktop platform features, not for its speed.

Architecture Differences

The two processors represent different architectural generations and process nodes. The 3820 is built on Sandy Bridge-E, using a 32nm process with 1,270 million transistors on a 294 mm² die, while the 3840QM is Ivy Bridge on 22nm with 1,400 million transistors on a much smaller 160 mm² die. This explains why the 3840QM achieves comparable performance at 45W versus 130W TDP — the smaller process node allows for higher transistor density and better power efficiency.

Both chips have 4 cores and 8 threads, with identical L1 (64 KB per core) and L2 (256 KB per core) cache sizes. The L3 cache differs: the 3820 has 10 MB shared, while the 3840QM has 8 MB shared. The 3820’s base clock is 3.60 GHz, but the 3840QM starts at 2.80 GHz; both boost to 3.80 GHz. The memory architecture diverges significantly, with the 3820 supporting quad-channel DDR3 at 51.2 GB/s bandwidth, whereas the 3840QM uses dual-channel DDR3 with no memory bandwidth figure provided. The 3840QM also features integrated Intel HD 4000 graphics, while the 3820 has none. The 3820 offers 40 PCIe Gen 2 lanes from the CPU, and its multiplier is unlocked, whereas the 3840QM’s multiplier is locked. The 3840QM’s transistor count is 10% higher, yet its die is nearly half the size, highlighting the process node advantage.

Where Each One Wins

Looking strictly at the head-to-head benchmark results, the Intel Core i7-3840QM wins all six Cinebench tests. The largest margin is in Cinebench R15 single-core, where the 3840QM scores 70 versus 69 for the 3820, a 1.4% difference. The other multi-core tests show tighter gaps: R15 multi-core is 498 versus 496 (0.4% delta), R20 multi-core is 2079 versus 2067 (0.6%), R23 multi-core is 4952 versus 4923 (0.6%), and the single-core R20 and R23 tests show 0.7% and 0.6% advantages respectively. The 3840QM’s wins are consistent but small, suggesting the newer architecture compensates for its lower base clock.

The 3820’s wins are not in raw benchmark scores but in platform capabilities. It offers quad-channel memory bandwidth of 51.2 GB/s, which the 3840QM cannot match with dual-channel support. The 3820 also provides 40 PCIe Gen 2 lanes, useful for multi-GPU or expansion-heavy desktop builds, and its unlocked multiplier allows overclocking, which the 3840QM’s locked multiplier prevents. For users who need integrated graphics, the 3840QM is the only choice since the 3820 has none. The 3820’s higher TDP of 130W suggests it may sustain boost clocks longer under heavy loads in a desktop chassis, but the benchmark data does not show this advantage in the tested Cinebench workloads.

FAQ

Q: Which processor is faster in multi-core Cinebench R23?

A: The Intel Core i7-3840QM scores 4952 points, beating the Intel Core i7-3820’s 4923 points by a 0.6% deltaPct.

Q: Does the 3820 have any performance advantage at all?

A: No. In the six head-to-head Cinebench tests, the 3820 loses all of them. Its nearest rival comparison shows it matches the Intel Xeon Bronze 3106 (0.1% delta) and Intel Core i7-3720QM (0.2% delta), but it trails the 3840QM in every measured benchmark.

Q: What is the memory bandwidth difference?

A: The 3820 supports quad-channel DDR3 with 51.2 GB/s bandwidth, while the 3840QM uses dual-channel DDR3 and has no memory bandwidth figure listed in the data.

Q: Can I overclock either processor?

A: The 3820 has an unlocked multiplier, while the 3840QM’s multiplier is locked. The data does not provide overclocking test results.

Q: Which processor has integrated graphics?

A: The 3840QM includes Intel HD 4000. The 3820 has no integrated graphics, requiring a discrete GPU.

Q: How do their average benchmark scores compare?

A: The 3820 has an average benchmark score of 1424, and the 3840QM has 1416. This puts the 3840QM 0.6% lower on average, despite winning the Cinebench tests, because the 3840QM’s Geekbench scores (2111 multi-core, 628 single-core) are included in its average but not in the head-to-head comparison.

Head-to-Head Benchmarks

The data reveals a consistent, narrow pattern of victories for the Intel Core i7-3840QM across all six Cinebench tests. The multi-core results are the closest: in Cinebench R15 multi-core, the 3840QM scores 498 versus 496 for the 3820, a 0.4% difference that is nearly negligible. The R20 multi-core test shows 2079 versus 2067, a 0.6% gap, and R23 multi-core shows 4952 versus 4923, also 0.6%. These margins are within the range of run-to-run variance for many systems, yet the consistency of the 3840QM’s wins across all tests suggests a real, if small, architectural edge.

The single-core results tell a similar story but with slightly larger margins. Cinebench R15 single-core has the 3840QM at 70 and the 3820 at 69, a 1.4% deltaPct. The R20 single-core test shows 293 versus 291 (0.7%), and R23 single-core shows 699 versus 695 (0.6%). The 3840QM’s higher boost clock of 3.80 GHz matches the 3820’s, but its newer Ivy Bridge architecture likely delivers higher instructions per clock, compensating for its 0.80 GHz lower base clock. The 3820’s larger 10 MB L3 cache versus 8 MB does not translate into a benchmark win, indicating that the cache size difference is less impactful than the architecture generation. Overall, the 3840QM’s six wins out of six tests are decisive but numerically tight, with no test exceeding a 1.4% deltaPct.

Specification Differences

The two processors differ in nearly every major specification category. The 3820 uses the Intel Socket 2011, while the 3840QM uses Intel BGA 1224, making them physically incompatible. The 3820 is a desktop part with a 130W TDP, and the 3840QM is a mobile part with a 45W TDP. The base clocks differ significantly: 3.60 GHz for the 3820 versus 2.80 GHz for the 3840QM, though both boost to 3.80 GHz. The process node favors the 3840QM at 22nm versus 32nm, and the transistor counts are 1,270 million for the 3820 and 1,400 million for the 3840QM. Die sizes are 294 mm² for the 3820 and 160 mm² for the 3840QM.

The cache hierarchy shows the 3820 with 10 MB shared L3 cache versus 8 MB on the 3840QM. Memory support is quad-channel on the 3820 with 51.2 GB/s bandwidth, while the 3840QM uses dual-channel with no bandwidth figure. The 3820 has 40 PCIe Gen 2 lanes from the CPU, while the 3840QM has no PCIe data listed. Integrated graphics are present only on the 3840QM (Intel HD 4000). The multiplier is unlocked on the 3820 but locked on the 3840QM. The 3820 launched on February 12, 2012 with a $305 launch MSRP, while the 3840QM launched on September 2, 2012 with no MSRP provided. The 3820 is marked as end-of-life, while the 3840QM’s production status is not specified. The 3820’s part number is SR0LD, and the 3840QM’s is SR0UU. Both lack ECC memory support.