Intel Core i5-8400T vs Intel Xeon E3-1585L v5 Comparison

The Verdict

The benchmark data is unambiguous: the Intel Xeon E3-1585L v5 wins every single head-to-head test against the Intel Core i5-8400T, taking all six comparisons with deltas ranging from -8.2% to -8.8% in its favor. The Xeon leads by roughly 8-9% in both single-core and multi-core Cinebench workloads across R15, R20, and R23. This is a consistent margin, not a fluke of one test methodology. The Core i5-8400T does counter with a higher average benchmark score of 2001 versus 1989 for the Xeon, but that aggregate figure is pulled up by Geekbench results where the i5 scored 1100 single-core and 4011 multi-core — tests the Xeon does not have listed. The Xeon’s higher clock speeds and hyper-threading overcome the i5’s two additional physical cores in every measured render workload.

For a buyer choosing strictly from the data, the Xeon E3-1585L v5 is the performance pick for threaded and single-threaded tasks alike, despite its lower core count. The Core i5-8400T, however, offers a lower TDP of 35 watts versus 45 watts, a desktop socket (Intel Socket 1151) versus the Xeon’s BGA 1440, and DDR4-only memory support. The i5 also has a launch MSRP of $182, while the Xeon’s launch MSRP is $445. If raw render performance is the priority, the Xeon wins outright. If power draw, socket flexibility, or cost efficiency matters more, the i5 has structural advantages that the benchmark scores do not capture. The Xeon’s percentile rank of 44 versus the i5’s 45 shows they sit nearly identically in the overall CPU distribution, so the margin between them is thin in the grand scheme — but in direct comparison, the Xeon is consistently ahead.

Architecture Differences

The two processors come from different architectural generations and physical designs. The Core i5-8400T is built on Coffee Lake, a 14 nm process from Intel, with a die size of 154 mm² and no listed transistor count. The Xeon E3-1585L v5 uses Skylake-H architecture, also on Intel’s 14 nm node, but with a larger die at 171 mm² and a documented 2,300 million transistors. The core configurations diverge sharply: the i5 has 6 cores and 6 threads, while the Xeon has 4 cores and 8 threads. This means the i5 has two extra physical cores but no hyper-threading, whereas the Xeon has fewer cores but uses simultaneous multi-threading to reach 8 threads total. The i5’s cache hierarchy includes 64 KB L1 per core, 256 KB L2 per core, and 9 MB shared L3. The Xeon matches the per-core L1 and L2 sizes but shares only 8 MB of L3. Both use dual-channel memory, but the i5 supports DDR4 exclusively with a memory bandwidth of 42.7 GB/s, while the Xeon supports both DDR3 and DDR4 at a lower bandwidth of 34.1 GB/s. The Xeon also enables ECC memory support, which the i5 lacks. Integrated graphics differ as well: the i5 ships with UHD Graphics 630, while the Xeon carries Iris Pro Graphics P580. The socket situation is another major split — the i5 uses a replaceable Intel Socket 1151, while the Xeon is soldered to BGA 1440, making it a non-upgradeable embedded part. The i5 was released in April 2018, while the Xeon predates it by nearly two years, launching in May 2016. Both are end-of-life parts with locked multipliers.

Head-to-Head Benchmarks

The Xeon’s sweep is methodical. In Cinebench R15 multi-core, the Xeon scores 693 against the i5’s 633, a delta of -8.7% for the i5. Single-core R15 tells the same story: 97 for the Xeon versus 89 for the i5, an 8.2% gap. Moving to Cinebench R20, the Xeon again leads multi-core with 2888 over 2638 (-8.7%) and single-core with 407 over 372 (-8.6%). The most recent Cinebench R23 results show the Xeon at 6878 multi-core and 971 single-core, while the i5 manages 6282 and 886 respectively, with deltas of -8.7% and -8.8%. The margins are remarkably tight across all tests, hovering between 8.2% and 8.8%. This consistency suggests the Xeon’s advantage comes from its higher base clock of 3.00 GHz versus 1.70 GHz and boost clock of 3.70 GHz versus 3.30 GHz. The i5’s extra two cores do not compensate for the Xeon’s clock speed and thread count advantage in these render workloads. Notably, the i5 has Geekbench results (1100 single-core, 4011 multi-core) that are not listed for the Xeon, so a direct Geekbench comparison is impossible from this data. The i5’s average benchmark score of 2001 edges out the Xeon’s 1989, but that figure is influenced by the Geekbench scores — without them, the i5’s Cinebench-only average would be lower. The data implies that in Cinebench, the Xeon is the clear victor, but the i5 may hold its own in other test suites where its core count matters more.

Specification Differences

| Field | Intel Core i5-8400T | Intel Xeon E3-1585L v5 |

|---|---|---|

| Cores | 6 | 4 |

| Threads | 6 | 8 |

| Base Clock | 1.70 GHz | 3.00 GHz |

| Boost Clock | 3.30 GHz | 3.70 GHz |

| TDP | 35 W | 45 W |

| Socket | Intel Socket 1151 | Intel BGA 1440 |

| Architecture | Coffee Lake | Skylake |

| Codename | Coffee Lake | Skylake-H |

| Die Size | 154 mm² | 171 mm² |

| Transistors | Not listed | 2,300 million |

| L3 Cache | 9 MB (shared) | 8 MB (shared) |

| Memory Support | DDR4 | DDR3, DDR4 |

| Memory Bandwidth | 42.7 GB/s | 34.1 GB/s |

| ECC Memory | No | Yes |

| Integrated Graphics | UHD Graphics 630 | Iris Pro Graphics P580 |

| Market Segment | Desktop | Server/Workstation |

| Release Date | 2018-04-01 | 2016-05-30 |

| Launch MSRP | $182 | $445 |

| Part Number | SR3X6 | SR2R9 |

FAQ

Q: Which CPU has more physical cores?

A: The Intel Core i5-8400T has 6 cores, while the Intel Xeon E3-1585L v5 has 4 cores.

Q: Which CPU has a higher boost clock?

A: The Xeon E3-1585L v5 boosts to 3.70 GHz, which is 0.40 GHz higher than the i5-8400T’s 3.30 GHz.

Q: Does the Xeon support ECC memory?

A: Yes, the Xeon E3-1585L v5 supports ECC memory, while the i5-8400T does not.

Q: Which CPU won more head-to-head benchmarks?

A: The Xeon E3-1585L v5 won all 6 head-to-head Cinebench tests, with deltas ranging from -8.2% to -8.8% against the i5.

Q: What is the TDP difference?

A: The i5-8400T has a 35 W TDP, while the Xeon E3-1585L v5 has a 45 W TDP, making the i5 more power-efficient on paper.

Q: Which CPU supports both DDR3 and DDR4 memory?

A: The Xeon E3-1585L v5 supports both DDR3 and DDR4, whereas the i5-8400T supports only DDR4.

Where Each One Wins

The Xeon E3-1585L v5 wins every benchmark where both are measured. Its advantages are most pronounced in single-core performance, where the gap reaches 8.8% in Cinebench R23, and multi-core, where it leads by 8.7% in R15, R20, and R23. The Xeon’s higher base and boost clocks, combined with hyper-threading, make it the stronger choice for any software that relies on Cinebench-style rendering or CPU-bound single-threaded tasks. Its ECC memory support and server/workstation market segment also point toward reliability-focused workloads like error-correcting data processing or long-running compute jobs. The Iris Pro Graphics P580 is a notable integrated GPU, though no benchmark data is provided to quantify its advantage.

The Core i5-8400T wins on structural grounds rather than benchmark scores. Its 35 W TDP makes it a lower-power option, which matters for thermally constrained systems or always-on machines. The desktop socket 1151 means it can be installed in standard motherboards and potentially upgraded, unlike the Xeon’s soldered BGA 1440. The i5 also supports faster memory bandwidth at 42.7 GB/s versus 34.1 GB/s, which could benefit memory-intensive applications even if the raw CPU render scores trail. Its two additional physical cores might help in workloads that scale with core count but are not captured in the listed Cinebench tests — the i5’s Geekbench multi-core score of 4011 suggests it has competitive strength outside the Cinebench suite, though no direct Xeon comparison exists. The i5’s lower launch MSRP of $182 versus $445 also positions it as the more accessible part, despite the Xeon’s performance lead. For users prioritizing power efficiency, socket flexibility, memory bandwidth, or cost, the i5 is the logical pick. For users who need the fastest Cinebench scores and ECC reliability, the Xeon is the clear winner.