AMD Phenom II X4 840T

The AMD Phenom II X4 840T is a four-core, four-thread desktop processor built on the K10 architecture with the Zosma codename, released in late August 2010 and now marked as end-of-life. It operates at a base clock of 2.90 GHz with a boost clock of 3.20 GHz, and the benchmark data places it near the bottom of the performance distribution, with a percentile of 17 among all CPUs. Its average benchmark score is 690, which effectively ties it with a small cluster of low-end Intel processors from different eras, making it a useful reference point for legacy multi-core workloads rather than a modern contender.

Benchmark Performance

The Phenom II X4 840T’s benchmark results show a clear pattern: multi-core scores are modest but internally consistent across Cinebench versions, while single-core scores are disproportionately low. In Cinebench R15 multi-core, the CPU scores 202; in R20 multi-core, it scores 842; and in R23 multi-core, it reaches 2006. These numbers scale roughly with the test’s increasing workload demands, indicating that the four physical cores are all being utilized without hyper-threading overhead. For single-core performance, the R20 score is 118, and the R23 single-core score is 283, which is notably weak compared to even budget dual-core chips from the same era.

When positioned against its nearest rivals, the average benchmark score of 690 places the 840T in a dead heat with the Intel Core m7-6Y75 (average score 690, delta -0.1%), the Intel Celeron G3920 (average score 689, delta +0.1%), the Intel Atom x7211RE (average score 691, delta -0.1%), and the Intel Celeron G4900 (average score 691, delta -0.1%). The delta percentages are all within 0.1% of zero, meaning that in aggregate multi-threaded performance, the 840T is statistically indistinguishable from these four rivals. However, the underlying workload characteristics differ: the m7-6Y75 is a low-power mobile chip, while the Celerons are desktop parts, so the equal scores mask divergent strengths in single-thread versus multi-thread tasks. The 17th percentile ranking underscores that the 840T sits in the lowest quintile of all CPUs ever benchmarked, which is expected for a processor from 2010 but still noteworthy for anyone considering it in a modern context.

Platform and Compatibility

The Phenom II X4 840T uses the AMD Socket AM3, which is a legacy platform that supports both DDR2 and DDR3 memory. The memory controller is dual-channel, providing a theoretical memory bandwidth of 21.3 GB/s, and ECC memory is not supported. This dual-memory compatibility is a distinctive feature of early AM3 processors, allowing motherboard manufacturers to offer boards with either DDR2 or DDR3 slots, though not simultaneously. The lack of ECC support means the 840T was aimed at mainstream desktop users rather than workstation or server environments.

PCIe support is Gen 2, which was the standard at the time of release. The processor itself has no integrated graphics; any display output relies on a discrete GPU or on certain motherboards that included a chipset-based integrated graphics solution. The part number is HD840TWFK4DGR, and the multiplier is locked, so overclocking is limited to adjusting the base clock or using motherboard-specific features such as AMD’s ACC (Advanced Clock Calibration) on compatible chipsets, though the locked multiplier prevents straightforward multiplier-based tuning. The upgrade path from this socket is essentially dead: AM3 was succeeded by AM3+ and then FM-socket families, so any system built around this CPU would require a full platform change to adopt modern processors.

Power and Thermals

The 840T carries a TDP of 95 watts, which places it in a mid-range power envelope for its generation. This TDP class implies that a standard tower air cooler with a 92mm or 120mm fan is sufficient for stock operation, and even a modest low-profile cooler could handle it in a well-ventilated case. The 45 nm process node from GlobalFoundries, with 904 million transistors on a 346 mm² die, contributes to this thermal profile; the die is relatively large by modern standards, but the clock speeds are low enough that heat density remains manageable.

For thermal management, the 95-watt TDP means that the CPU does not require exotic cooling solutions. A capable air cooler with a direct-contact heat pipe design would keep temperatures within safe limits under sustained multi-core loads, as evidenced by the Cinebench scores being reproducible without throttling. However, because the multiplier is locked, any enthusiast tuning would rely on raising the base clock, which increases both frequency and power draw, potentially pushing the effective TDP beyond the rated 95 watts. In that scenario, a more robust cooler with a larger heatsink or higher airflow would be prudent, but the data does not suggest that stock operation poses any thermal challenge.

FAQ

Q: What is the average benchmark score of the AMD Phenom II X4 840T?

A: The average benchmark score is 690, placing it in the 17th percentile among all CPUs.

Q: How does the 840T compare to the Intel Celeron G3920 in average score?

A: The 840T scores 690, while the Celeron G3920 scores 689, resulting in a delta of +0.1% in favor of the 840T.

Q: What memory types does the 840T support?

A: It supports both DDR2 and DDR3 memory, running in dual-channel mode with a theoretical bandwidth of 21.3 GB/s.

Q: Is the multiplier on the 840T unlocked for overclocking?

A: No, the multiplier is locked, so overclocking would require adjusting the base clock instead.

Q: Does the 840T have integrated graphics?

A: No, the processor itself has no integrated graphics; display output requires a discrete GPU or a motherboard with chipset-based graphics.

Q: What is the TDP of the 840T, and what cooling does it imply?

A: The TDP is 95 watts, which implies that a standard tower air cooler is sufficient for stock operation.

How It Compares

Against the Intel Core m7-6Y75, the 840T matches its average score of 690 with a delta of -0.1%. The m7-6Y75 is a low-power mobile chip, so the equal score suggests that the 840T’s four cores can offset the m7’s higher per-core efficiency in multi-threaded tests, but the m7 would likely dominate in single-thread workloads due to its newer architecture.

The Intel Celeron G3920 presents a near-identical average score of 689, with the 840T leading by just 0.1%. The G3920 is a dual-core desktop part, so the 840T’s advantage in core count is roughly canceled by the Celeron’s higher clock speeds and newer architecture, making them equivalent in aggregate performance.

The Intel Atom x7211RE scores 691, edging out the 840T by 0.1%. This Atom is a low-power embedded-oriented chip, so the close score indicates that the 840T’s older K10 cores are only marginally competitive with modern low-power designs in multi-threaded synthetic workloads, and likely far behind in efficiency.

The Intel Celeron G4900 also scores 691, giving the 840T a -0.1% delta. The G4900 is a dual-core Coffee Lake-era part, and its higher single-core performance compensates for having fewer cores, resulting in a statistical tie that would break differently depending on the workload — the 840T wins in heavily threaded tasks, while the G4900 wins in lightly threaded ones.

Single-Thread vs Multi-Thread Behavior

The data reveals a stark contrast between single-core and multi-core performance. In Cinebench R20, the single-core score is 118, while the multi-core score is 842, yielding a multi-to-single ratio of roughly 7.1x. That ratio is far higher than the theoretical 4x scaling from four cores, which indicates that the single-core performance is severely bottlenecked by the K10 architecture’s low instruction-per-clock efficiency and modest 2.90 GHz base clock. In Cinebench R23, the single-core score of 283 against a multi-core score of 2006 gives a ratio of about 7.1x as well, confirming a consistent pattern.

For real workloads, this split means that the 840T is disproportionately better at tasks that can utilize all four cores, such as video encoding, 3D rendering, or batch image processing. A single-threaded application, like a legacy game or a spreadsheet recalculation, would see performance comparable to a modern low-end dual-core CPU, because the single-core score is so low. The 3.20 GHz boost clock helps slightly, but it cannot overcome the architectural limitations. Consequently, the 840T is a poor choice for daily desktop use where responsiveness often depends on single-thread speed, but it retains some utility for parallel batch workloads where the four cores can be fully engaged. The percentile of 17 reflects this overall weakness, as most modern CPUs, even budget ones, deliver far better single-thread performance, dragging the aggregate score down despite the multi-core showing.