CPU Comparison

The Intel Xeon E5645 and Intel Xeon D-1527 are separated by five years of silicon evolution, yet benchmark results show they land in nearly the same performance tier. The older Westmere-EP chip wins all six head-to-head Cinebench tests, but the margins are razor-thin, never exceeding 0.4%. The data indicates the E5645 edges out the D-1527 in every single-core and multi-core workload tested, while the D-1527 counters with a 14 nm process, DDR4 support, and a 35 W TDP that is less than half the E5645’s 80 W figure. For raw compute, the E5645 is the statistical winner; for efficiency and platform longevity, the D-1527 is the clear choice.

The Verdict

The benchmark data points to a decision based on workload priorities rather than outright performance. The Intel Xeon E5645 wins every Cinebench test in the head-to-head comparison, from the R15 multicore score of 421 versus 420 to the R23 multicore score of 4187 versus 4176. These wins are consistent but marginal, the largest delta is 0.4% in Cinebench R20 single-core. If your work is purely CPU-bound rendering or batch processing, the E5645 technically delivers more throughput, but the difference is negligible in real-world terms.

The Intel Xeon D-1527, however, offers a more compelling modern platform story. It uses a 14 nm process versus the E5645’s 32 nm node, supports both DDR3 and DDR4 memory (the E5645 is DDR3-only), and runs on PCIe Gen 3 with 24 lanes versus the E5645’s Gen 2. The D-1527’s 35 W TDP makes it dramatically more power-efficient than the 80 W E5645, which matters in dense server deployments. It is also an active production part, while the E5645 is end-of-life.

Who should pick which? Choose the E5645 if you have a Socket 1366 platform already in place and need six cores and twelve threads at a 2.40 GHz base clock. Choose the D-1527 if you are building a new system and prioritize lower power draw, a smaller BGA 1667 footprint, and modern memory/PCIe standards, accepting a slight performance deficit that the data shows is under half a percent in every test.

FAQ

Q: Which CPU has higher single-core performance?

A: The Intel Xeon E5645 wins all three single-core tests, but by the narrowest margins. In Cinebench R15, both score 59; in R20, the E5645 scores 248 versus 247; in R23, it scores 591 versus 589. The largest single-core delta is 0.4%.

Q: How do their multi-core scores compare?

A: The E5645 leads in every multi-core test. Cinebench R15 shows 421 versus 420, R20 shows 1758 versus 1753, and R23 shows 4187 versus 4176. The E5645’s advantage ranges from 0.2% to 0.3%.

Q: Do both CPUs support ECC memory?

A: Yes, both the Intel Xeon E5645 and the Intel Xeon D-1527 list ECC memory support in their specifications. However, the D-1527 supports both DDR3 and DDR4, while the E5645 is limited to DDR3.

Q: What is the TDP difference and why does it matter?

A: The Intel Xeon E5645 has an 80 W TDP, while the Intel Xeon D-1527 has a 35 W TDP. This means the D-1527 draws less than half the power, which directly impacts cooling requirements and operating costs in servers.

Q: Which CPU has a higher boost clock?

A: The Intel Xeon D-1527 has a boost clock of 2.70 GHz, slightly higher than the E5645’s 2.67 GHz. Despite this, the E5645 still wins all single-core benchmarks.

Q: Are these CPUs comparable in overall benchmark standing?

A: Both sit at the 34th percentile among all CPUs. Their average benchmark scores are 1211 for the E5645 and 1207 for the D-1527, with the E5645 landing 0.3% ahead in the head-to-head comparison.

Architecture Differences

The two processors come from completely different architectural eras. The Intel Xeon E5645 uses Westmere-EP, a 32 nm design with 1,170 million transistors on a 239 mm² die. It is built on the Intel Socket 1366 platform and belongs to the first-generation Xeon lineup. The D-1527, in contrast, is a Broadwell-DE part fabricated on a 14 nm process, packing 3,200 million transistors into a 246 mm² die. This is a fundamental shift: the newer node allows roughly 2.7 times more transistors in nearly the same die area.

Cache topology differs significantly. The E5645 has a shared 12 MB L3 cache, while the D-1527 uses a per-core L3 arrangement of 1.5 MB per core. With four cores, the D-1527’s total L3 is effectively 6 MB, but the per-core allocation suggests different access patterns. Both have the same per-core L1 (64 KB) and L2 (256 KB) sizes.

The memory architecture also diverges. The E5645 supports only DDR3 with a triple-channel memory bus, while the D-1527 supports both DDR3 and DDR4 with a dual-channel bus. The D-1527’s PCIe implementation is newer: Gen 3 with 24 lanes from the CPU, versus Gen 2 on the E5645. The D-1527 also uses a BGA 1667 socket, which is soldered rather than socketed, whereas the E5645 uses the traditional Socket 1366.

Production status tells a story of lifecycle. The E5645 is end-of-life, released in March 2010. The D-1527 is active, released in October 2015. The D-1527 is the only one with a launch MSRP of $213. The E5645 has no listed launch MSRP.

Specification Differences

The core count is the most obvious difference: the E5645 has 6 cores and 12 threads, while the D-1527 has 4 cores and 8 threads. Base clocks are 2.40 GHz for the E5645 and 2.20 GHz for the D-1527, but the boost clocks reverse that order, 2.67 GHz versus 2.70 GHz.

The TDP gap is stark: 80 W for the E5645 versus 35 W for the D-1527. This is a 45 W difference that affects cooling and power delivery. The E5645 uses Intel Socket 1366, while the D-1527 uses Intel BGA 1667.

Process node and transistor count differ as noted: 32 nm with 1,170 million transistors versus 14 nm with 3,200 million transistors. The die sizes are close (239 mm² versus 246 mm²), but the transistor density is dramatically higher on the D-1527.

Memory support, PCIe generation, and lane counts all favor the D-1527. The E5645 is limited to DDR3 and triple-channel memory; the D-1527 handles DDR3 and DDR4 with dual-channel. PCIe Gen 2 on the E5645 versus Gen 3 with 24 lanes on the D-1527. Both have unlocked multipliers set to false, both lack integrated graphics, and both support ECC memory.

The production status is a key differentiator: the E5645 is end-of-life, while the D-1527 is active. The part numbers differ (SLBWZ for the E5645, SR2DK for the D-1527), and only the D-1527 has a launch MSRP of $213.

Head-to-Head Benchmarks

The head-to-head results are remarkably consistent: the Intel Xeon E5645 wins all six tests, but every victory is by less than half a percentage point. In Cinebench R15 multicore, the E5645 scores 421 against the D-1527’s 420, a 0.2% delta. Single-core R15 is a tie at 59 points each.

Cinebench R20 shows a similar pattern. The E5645 takes multicore with 1758 versus 1753 (0.3% delta) and single-core with 248 versus 247 (0.4% delta). Cinebench R23 repeats the trend: 4187 versus 4176 in multicore (0.3% delta) and 591 versus 589 in single-core (0.3% delta).

These numbers suggest that despite having two fewer cores, the D-1527’s newer architecture and higher boost clock largely compensate for the core deficit. The D-1527’s 2.70 GHz boost is 0.03 GHz higher than the E5645’s 2.67 GHz, yet it still loses every test. The wins for the E5645 are real but statistically insignificant, the largest margin is 0.4%, which could easily be within run-to-run variance.

The average benchmark scores confirm the closeness. The E5645 has an average score of 1211, while the D-1527 sits at 1207. The E5645’s nearest rival is the Intel Core i3-7300T at 1211 with a 0% delta, and the D-1527’s nearest rival is the Intel Xeon D-1520 at 1209 with a -0.1% delta. Both CPUs occupy the same 34th percentile in the overall CPU ranking.

Where Each One Wins

The Intel Xeon E5645 wins on raw benchmark scores across the board. It is the better choice for applications where every point of Cinebench performance matters, such as single-threaded legacy workloads or multi-threaded rendering that can use all 12 threads. The data shows a 0.2% to 0.4% advantage in every test, which, while small, is consistent.

The Intel Xeon D-1527 wins on platform efficiency and modern features. Its 35 W TDP is less than half the E5645’s 80 W, making it superior for power-constrained environments. It supports DDR4 memory, which offers higher bandwidth potential than the E5645’s DDR3-only limitation. The PCIe Gen 3 with 24 lanes provides double the bandwidth of the E5645’s Gen 2, which matters for NVMe storage or high-speed networking.

For new deployments, the D-1527 is the practical choice. It is an active product with a known launch MSRP of $213, while the E5645 is end-of-life. The D-1527’s BGA form factor is designed for compact, low-power systems, whereas the E5645 requires a larger Socket 1366 motherboard.

For legacy upgrades, the E5645 makes sense if you already own a Socket 1366 board. Its six cores provide more parallel throughput than the D-1527’s four, and the benchmark data confirms this advantage. The E5645’s 12 MB shared L3 cache versus the D-1527’s per-core 1.5 MB arrangement may also favor workloads with shared data sets.

In summary, the E5645 is the performance winner in every measured test, but the D-1527 is the better modern platform. The benchmark deltas are so small that real-world performance will be nearly identical; the decision should hinge on power, memory support, and platform availability rather than the 0.3% average performance gap.