AMD Athlon II X4 638

The AMD Athlon II X4 638 is a quad-core desktop processor built on the K10 architecture, fabricated on a 32 nm process at GlobalFoundries. It occupies the 50th percentile among all CPUs in the database, placing it squarely in the mid-range of historical desktop parts. With a base clock of 2.70 GHz and no boost capability, this chip relies entirely on its four physical cores and per-core cache design to deliver performance.

Benchmark Performance

The benchmark data for the Athlon II X4 638 is limited — the average benchmark score is 0, and there are no individual benchmark entries recorded. This absence of direct scores means that performance characterization must rely on architectural indicators rather than measured results. The processor’s 50th percentile ranking against all CPUs suggests a median position: roughly half of all processors in the database outperform it, and half underperform it.

Without nearestRivals data or specific score deltas, the analysis cannot cite exact percentage differences versus competing parts. However, the structural facts are telling. The chip features four cores and four threads, meaning no simultaneous multithreading — each core handles exactly one thread. The base clock of 2.70 GHz is modest by modern standards, but for its era, the combination of four cores at that frequency would typically place it in the entry-to-mid mainstream segment.

The processor’s cache hierarchy is notable: 128 KB of L1 per core and 1 MB of L2 per core, with no L3 cache present. This per-core L2 arrangement means each core has direct access to its own 1 MB block, which can reduce contention in multi-threaded workloads compared to shared-cache designs. However, the lack of any shared L3 cache means inter-core communication relies on the memory subsystem, which is limited by the dual-channel DDR3 interface.

Platform and Compatibility

The Athlon II X4 638 uses the AMD Socket FM1, which is tied to the Llano architecture generation. This socket supports DDR3 memory in a dual-channel configuration, providing a theoretical memory bandwidth of 29.9 GB/s. ECC memory is not supported, so this processor targets consumer desktop builds rather than workstation or server environments.

PCIe support is Gen 2, which was standard for its release period. The processor does not include integrated graphics — the fact pack lists no iGPU — so a discrete graphics card is required for any display output. The socket FM1 platform is end-of-life, meaning upgrade paths are limited to other FM1 processors from the same generation. There is no cross-generation upgrade possibility; moving to a newer AMD platform would require a new motherboard and memory.

The processor has a locked multiplier, so overclocking via multiplier adjustment is not available. Enthusiasts seeking frequency tuning would need to rely on base clock adjustments, which affect the entire platform and are generally less stable. The part number AD638XOJZ43GXAD638XOJGXBOX indicates a boxed retail variant, but no launch MSRP is provided in the data.

How It Compares

The nearestRivals array is empty in the fact pack, so there are no direct competitor scores or deltaPct values to reference. This absence is itself informative: the database does not currently hold comparative benchmark data for this processor against specific rivals. Without rival names or percentage deltas, the comparison must be framed qualitatively.

Given the 50th percentile ranking, the Athlon II X4 638 would sit near the median of all CPUs ever benchmarked in this database. For a quad-core part without SMT and with a 2.70 GHz base clock, this placement suggests it competes with other early-2010s mainstream quad-cores. The lack of boost clock means single-thread performance is fixed at 2.70 GHz, which would trail any rival that offers dynamic frequency scaling. Multi-threaded workloads, however, benefit from the four full cores, which can hold their own against dual-core parts with higher clocks but fewer threads.

The 32 nm process and 1,178 million transistors on a 228 mm² die indicate a mid-size chip for its node. The absence of L3 cache is a notable differentiator — many contemporary rivals included shared L3 to improve performance in cache-sensitive workloads. This processor’s per-core L2 design may excel in applications that exhibit high locality within a single thread, but it could lag in workloads that repeatedly access shared data across cores.

FAQ

Q: What socket does the AMD Athlon II X4 638 use?

A: It uses AMD Socket FM1, which is associated with the Llano architecture generation.

Q: Does this processor support ECC memory?

A: No, ECC memory is not supported. The memory support is limited to non-ECC DDR3.

Q: How much L2 cache does each core have?

A: Each core has 1 MB of L2 cache, totaling 4 MB across all four cores. There is no L3 cache.

Q: Is the multiplier unlocked for overclocking?

A: No, the multiplier is locked. Overclocking would require base clock adjustments, which are not officially supported.

Q: What is the memory bandwidth of this processor?

A: The dual-channel DDR3 memory bus provides a theoretical bandwidth of 29.9 GB/s.

Q: Does the Athlon II X4 638 include integrated graphics?

A: No, the fact pack lists no integrated graphics, so a discrete GPU is necessary for display output.

Power and Thermals

The thermal design power (TDP) is 65 watts, which places this processor in the mainstream efficiency class for its era. A 65 W TDP allows for relatively modest cooling solutions — a stock cooler or a low-profile air cooler would typically suffice for standard operation. The 32 nm process node contributes to this moderate power draw, as smaller transistors generally reduce switching losses compared to larger nodes.

Given the 65 W envelope and the absence of a boost clock, peak power consumption is likely to remain close to the TDP under sustained all-core loads. The four cores at 2.70 GHz do not push the chip into high-power territory, which also means thermals should stay manageable in well-ventilated cases. Enthusiasts might still opt for an aftermarket cooler to reduce noise, but the data indicates that a capable air cooler is sufficient — no liquid cooling or high-end tower is implied by the 65 W class.

The die size of 228 mm² and transistor count of 1,178 million suggest a moderately dense chip, but the modest clock speeds keep power density in check. For budget builds of its time, this processor would pair naturally with entry-level motherboards and standard power supplies, though the fact pack does not provide wattage figures for the latter.

Single-Thread vs Multi-Thread Behavior

The Athlon II X4 638 has a fixed base clock of 2.70 GHz with no boost clock, meaning single-thread performance is constant across all conditions. This is a significant limitation in modern workloads that are often single-thread-bound, such as older games or lightly threaded applications. Without frequency scaling, the processor cannot temporarily elevate performance for short bursts, so single-thread tasks will see consistent but unremarkable throughput.

Multi-threaded behavior is where this chip’s design shines relatively. Four physical cores, each with 1 MB of dedicated L2 cache, can handle parallel workloads without sharing cache resources. Threads that operate independently benefit from this isolation, avoiding the cache thrashing that can occur in shared-cache designs. However, the lack of SMT means that each core handles exactly one thread — there is no extra thread-level parallelism per core.

The per-core L2 cache of 1 MB is generous for its generation, which helps in workloads with moderate working sets that fit within each core’s private cache. Conversely, the absence of L3 cache means that data shared across cores must go through the dual-channel DDR3 memory, capped at 29.9 GB/s. This becomes a bottleneck in highly parallel tasks that repeatedly access common data structures, such as database queries or certain scientific simulations. The 50th percentile ranking reflects this mixed profile: strong for its time in multi-threaded throughput among quad-cores, but held back by fixed clocks and no shared cache in single-thread and cache-sensitive scenarios.