Intel Xeon D-1521 vs Intel Xeon E3-1226 v3 Comparison

The Intel Xeon D-1521 and the Intel Xeon E3-1226 v3 are both quad-core server processors, yet the data reveals two very different design philosophies. The D-1521 is a low-power, highly integrated system-on-a-chip built on a modern 14 nm process, while the E3-1226 v3 is a more traditional, higher-clocked socketed CPU from the previous generation. Benchmark results show a remarkable parity in raw compute performance, but the underlying architectures and platform implications tell a more nuanced story.

Where Each One Wins

Based strictly on the head-to-head benchmark data, the Intel Xeon D-1521 wins every single test. It takes the Cinebench R15 multicore test with a score of 476 against 472 for the E3-1226 v3, a 0.8% advantage. The single-core R15 result is 67 versus 66, a 1.5% lead for the D-1521. This pattern continues across newer benchmarks: in Cinebench R20, the D-1521 scores 1985 versus 1970 in multicore (0.8% ahead) and 280 versus 278 in single-core (0.7% ahead). The R23 results mirror this, with the D-1521 leading 4728 to 4692 in multicore and 667 to 662 in single-core, both by 0.8%.

The wins are consistent but narrow, never exceeding a 1.5% delta. This indicates that in purely computational throughput, neither processor has a meaningful edge. The D-1521's victory confirms its more efficient architecture and hyper-threading, which allows it to process 8 threads simultaneously compared to the E3-1226 v3's 4 threads. However, the E3-1226 v3 compensates with significantly higher clock speeds—a 3.30 GHz base and 3.70 GHz boost versus the D-1521's 2.40 GHz and 2.70 GHz. The practical conclusion is that the D-1521 wins in every measured benchmark, but the margin is so thin that real-world applications would likely see identical performance.

The real differentiator is not performance but platform. The D-1521 uses a BGA 1667 socket, meaning it is soldered to the motherboard, while the E3-1226 v3 uses the LGA 1150 socket, allowing for processor upgrades. The D-1521 also offers 24 PCIe Gen 3 lanes versus 16 on the E3-1226 v3, and supports both DDR3 and DDR4 memory, whereas the E3-1226 v3 only supports DDR3. These factors make the D-1521 a more flexible and future-proof option for dense server deployments, while the E3-1226 v3 fits into existing socket 1150 infrastructure.

Architecture Differences

The architectural gap between these two processors is substantial. The Intel Xeon D-1521 is built on the Broadwell architecture using a 14 nm process node, while the Intel Xeon E3-1226 v3 uses the older Haswell architecture on a 22 nm process. This process shrink allows the D-1521 to pack 3,200 million transistors into a 246 mm² die, compared to the E3-1226 v3's 1,400 million transistors on a 160 mm² die. The D-1521 comes from the "Broadwell-DE" generation, designed specifically for low-power, high-density server environments, while the E3-1226 v3 is from the "Haswell-WS" generation, targeting traditional workstation and server builds.

Cache configuration is another key difference. The D-1521 has a per-core cache layout: 64 KB of L1 and 256 KB of L2 per core, with 1.5 MB of L3 per core. This results in a total of 6 MB of L3 cache across the four cores, but it is distributed rather than shared. The E3-1226 v3, conversely, uses a shared 8 MB L3 cache, which can be accessed by all cores simultaneously. This shared cache design is often more efficient for workloads that require frequent inter-core communication, though the D-1521's newer process and higher transistor count may compensate.

The D-1521 also includes integrated memory controllers for both DDR3 and DDR4, while the E3-1226 v3 is limited to DDR3 with a specified memory bandwidth of 25.6 GB/s. The D-1521 has no listed memory bandwidth figure, but its support for DDR4 suggests higher potential throughput. Additionally, the E3-1226 v3 includes Intel HD P4600 integrated graphics, which the D-1521 lacks entirely. This makes the E3-1226 v3 a viable option for systems without a discrete GPU, while the D-1521 requires external graphics. The E3-1226 v3 also has a higher TDP of 84 watts versus 45 watts for the D-1521, reflecting its higher clock speeds and older process technology.

FAQ

Q: Which processor has more threads?

A: The Intel Xeon D-1521 has 8 threads thanks to hyper-threading on its 4 cores, while the Intel Xeon E3-1226 v3 has only 4 threads for its 4 cores. This gives the D-1521 a theoretical advantage in heavily threaded workloads, as confirmed by its narrow but consistent multicore benchmark wins.

Q: Do both processors support ECC memory?

A: Yes, both the Intel Xeon D-1521 and the Intel Xeon E3-1226 v3 support ECC memory. This is a critical feature for server and workstation reliability, and both CPUs are marketed for the Server/Workstation segment.

Q: What is the difference in socket types?

A: The Intel Xeon D-1521 uses the Intel BGA 1667 socket, which means it is permanently soldered to the motherboard. The Intel Xeon E3-1226 v3 uses the Intel Socket 1150, a standard LGA socket that allows the processor to be removed and replaced.

Q: Which processor has integrated graphics?

A: Only the Intel Xeon E3-1226 v3 has integrated graphics, specifically the Intel HD P4600. The Intel Xeon D-1521 has no integrated graphics, so a discrete GPU is required for any display output.

Q: What memory types are supported?

A: The Intel Xeon D-1521 supports both DDR3 and DDR4 memory, while the Intel Xeon E3-1226 v3 supports only DDR3. Both use a dual-channel memory bus, but the D-1521's DDR4 support offers a potential bandwidth upgrade path.

Q: How do their production statuses compare?

A: The Intel Xeon D-1521 is listed as "Active" production status, meaning it is still being manufactured and sold. The Intel Xeon E3-1226 v3 is marked as "End-of-life," indicating it has been discontinued by Intel.

Specification Differences

The two processors differ in several key specification fields. The base clock speed is a major divergence: the E3-1226 v3 runs at 3.30 GHz compared to the D-1521's 2.40 GHz. Boost clocks follow the same pattern, with the E3-1226 v3 reaching 3.70 GHz versus 2.70 GHz for the D-1521. This gives the E3-1226 v3 a 37.5% higher base clock and a 37% higher boost clock, which explains why it can nearly match the D-1521 despite having half the threads.

The TDP is another clear difference, with the D-1521 drawing only 45 watts compared to the E3-1226 v3's 84 watts. This 39-watt gap makes the D-1521 significantly more power-efficient, which is crucial for dense server racks. The process node also differs: 14 nm for the D-1521 versus 22 nm for the E3-1226 v3. Transistor count and die size follow this trend, with the D-1521 containing 3,200 million transistors on a 246 mm² die versus 1,400 million on 160 mm² for the E3-1226 v3.

Memory support is a categorical difference: the D-1521 supports DDR3 and DDR4, while the E3-1226 v3 only supports DDR3. The E3-1226 v3 has a listed memory bandwidth of 25.6 GB/s, while the D-1521 has no figure listed. PCIe lane count also differs, with the D-1521 offering 24 Gen 3 lanes versus 16 Gen 3 lanes on the E3-1226 v3. The release dates are about 17 months apart, with the E3-1226 v3 launching in May 2014 and the D-1521 in October 2015. The launch MSRP for the D-1521 is $199, and for the E3-1226 v3 it is $213.

Head-to-Head Benchmarks

The benchmark data presents a clear, if narrow, sweep for the Intel Xeon D-1521. In Cinebench R15 multicore, the D-1521 scores 476 against 472 for the E3-1226 v3, a 0.8% difference. The single-core R15 test shows a larger relative gap of 1.5%, with scores of 67 and 66 respectively. This suggests the D-1521 has better single-thread efficiency per clock, despite its lower frequency.

Moving to Cinebench R20, the multicore scores are 1985 for the D-1521 and 1970 for the E3-1226 v3, again a 0.8% lead. The single-core R20 scores are 280 versus 278, a 0.7% margin. The R23 benchmarks continue this trend: multicore scores of 4728 and 4692 (0.8% delta) and single-core scores of 667 and 662 (0.8% delta). Across all six tests, the D-1521 wins every time, but the average delta is under 1%, making the performance difference statistically negligible for most applications.

The most significant win for the D-1521 is in the R15 single-core test, where it achieves a 1.5% lead. This is curious given the E3-1226 v3's much higher clock speed. It implies that the D-1521's Broadwell architecture has a superior instructions-per-clock rate, allowing it to overcome a 1 GHz frequency deficit. Conversely, the closest contest is in R20 single-core, where the D-1521 leads by only 0.7%. The multicore results consistently show a 0.8% advantage, which aligns with the D-1521's 8 threads versus 4 threads, but the small magnitude suggests that the E3-1226 v3's high clocks nearly neutralize that thread advantage.

The Verdict

From the data, the Intel Xeon D-1521 is the better processor for new server deployments where power efficiency and platform flexibility are priorities. Its 45-watt TDP, support for both DDR3 and DDR4, and 24 PCIe lanes make it a more versatile building block for dense, modern systems. It wins every benchmark, albeit by a slim margin, and carries an "Active" production status with a lower launch MSRP of $199 versus $213 for the E3-1226 v3.

The Intel Xeon E3-1226 v3, despite being end-of-life, still holds appeal for specific scenarios. Its higher clock speeds (3.30 GHz base, 3.70 GHz boost) make it a strong choice for lightly threaded workloads where raw frequency matters more than thread count. It also includes integrated graphics, eliminating the need for a separate GPU in basic server or workstation builds. For those with existing Socket 1150 motherboards, it offers a drop-in upgrade path that the BGA 1667 D-1521 cannot match.

The data suggests that for most modern applications, the D-1521 is the superior choice due to its efficiency, memory flexibility, and slightly better benchmark scores. The E3-1226 v3 is a capable but aging alternative, best suited for legacy systems or scenarios requiring integrated graphics and maximum single-core frequency. The performance difference between them is so small that platform considerations should ultimately drive the decision.