GPU Comparison

The NVIDIA Tesla K40c and NVIDIA T400 represent two very different eras of GPU design, and the benchmark data reflects that. In the single available head-to-head test, the Tesla K40c edges out the T400 by 2.5% in Geekbench OpenCL, scoring 17,468 against 17,039. While this is a narrow margin, it is notable given the architectural chasm between the two parts. The K40c also holds a slight overall percentile lead, sitting at the 61st percentile of all GPUs compared to the T400’s 60th. However, the T400 counters with a Vulkan score of 15,976, a test the K40c does not have a recorded result for, and it achieves a higher average benchmark score of 16,508 when accounting for both of its tested APIs.

Head-to-Head Benchmarks

The only direct comparison available is Geekbench OpenCL, where the Tesla K40c wins with 17,468 points versus the T400’s 17,039. That 2.5% delta is within the margin of error for many synthetic workloads, but it still places the older card ahead. Interestingly, the K40c’s nearest rivals in the broader database are all within a 1% range: the AMD Radeon Pro 460 (17,509, -0.2%), the AMD Radeon Pro 560 (17,551, -0.5%), the AMD Radeon 780M (17,588, -0.7%), and the NVIDIA GeForce RTX 4060 (17,639, -1%). This cluster indicates that the K40c is competing with much newer, more efficient parts, despite its age.

The T400, by contrast, sits in a different competitive neighborhood. Its OpenCL score of 17,039 places it near the NVIDIA GeForce RTX 5090 D V2 (16,504, 0% delta), the AMD Radeon PRO W7500 (16,415, 0.6%), the NVIDIA RTX PRO 6000 Blackwell (16,408, 0.6%), and the AMD Radeon RX 5700 XT (16,361, 0.9%). The fact that a low-power Turing workstation card is trading blows with flagship and high-end consumer cards in this specific Geekbench test suggests the workload is not purely compute-bound. The T400’s Vulkan result of 15,976 further shows its API versatility, though no direct K40c counterpart exists for that test.

Architecture Differences

The foundational difference is the architecture generation. The Tesla K40c uses the GK180 chip on the Kepler architecture, built on TSMC’s 28 nm process. It packs 7,080 million transistors into a 561 mm² die, yielding a transistor density of 12.6 million per mm². The T400 uses the TU117 chip on the Turing architecture, fabricated on TSMC’s 12 nm process, with 4,700 million transistors on a 200 mm² die, achieving 23.5 million transistors per mm². This means the T400 is nearly twice as dense, reflecting the process improvements.

Clock speeds tell a stark story. The K40c has a base clock of 745 MHz and a boost of 876 MHz, while the T400 starts at a low 420 MHz base but boosts to 1,425 MHz. The T400’s boost clock is 62.7% higher than the K40c’s, which helps offset its smaller hardware footprint. The K40c’s memory runs at 1,502 MHz (6 Gbps effective) over a 384-bit bus, providing 288.4 GB/s of bandwidth. The T400 uses 1,250 MHz (10 Gbps effective) GDDR6 over a 64-bit bus, yielding only 80.00 GB/s. That is a 72.3% reduction in memory bandwidth, a critical gap for many compute workloads.

The shading resources are heavily skewed toward the K40c. It has 2,880 shading units, 240 texture mapping units, and 48 ROPs. The T400 has just 384 shading units, 24 TMUs, and 16 ROPs. Consequently, the K40c achieves a pixel rate of 52.56 GPixel/s and a texture rate of 210.2 GTexel/s, versus the T400’s 22.80 GPixel/s and 34.20 GTexel/s. The FP32 compute is 5.046 TFLOPS for the K40c against 1,094.4 GFLOPS (approximately 1.09 TFLOPS) for the T400, a 4.6x advantage for the older card. The T400 does have FP16 capability at 2.189 TFLOPS (2:1), which the K40c lacks entirely.

Where Each One Wins

The Tesla K40c is the clear winner in raw compute throughput. Its 5.046 TFLOPS FP32 performance, 288.4 GB/s memory bandwidth, and 12 GB of GDDR5 memory make it suited for large-scale scientific computing, deep learning inference, and any workload that can saturate a 384-bit memory bus. The 12 GB capacity is six times larger than the T400’s 2 GB, which is decisive for datasets that exceed 2 GB. The K40c’s texture and pixel rates are also far superior, meaning it will dominate in graphics tasks that rely on fill-rate, such as high-resolution rendering or multi-sampled anti-aliasing.

The T400 wins on efficiency and modern feature support. Its 30 W TDP is a fraction of the K40c’s 245 W, and it requires no external power connectors, drawing entirely from the PCIe slot. The K40c needs a 1x 6-pin and 1x 8-pin connector, plus a 550 W suggested PSU, versus the T400’s 200 W suggestion. The T400 also has display outputs (3x mini-DisplayPort 1.4a), while the K40c has none, making the T400 usable for desktop output. The T400 supports DirectX 12 (12_1) and Vulkan 1.4, while the K40c is limited to DirectX 12 (11_0) and Vulkan 1.2.175. For modern API features, the T400 is the more future-proof option.

The T400’s higher boost clock (1,425 MHz vs 876 MHz) and FP16 support also give it an edge in workloads that are latency-sensitive or that can leverage half-precision arithmetic. Its Vulkan score of 15,976 indicates it can handle modern graphics APIs efficiently, a capability the K40c was never designed for. In a dual-slot versus single-slot comparison, the T400 is far easier to integrate into small form-factor systems.

FAQ

Q: Which card has higher raw compute performance in FP32?

A: The Tesla K40c is decisively ahead, delivering 5.046 TFLOPS FP32, compared to the T400’s 1,094.4 GFLOPS. This is a 4.6x difference in raw single-precision throughput.

Q: Does the T400 have any compute advantage over the K40c?

A: Yes, in FP16. The T400 supports FP16 at 2.189 TFLOPS (2:1), while the K40c has no FP16 capability listed. For workloads that can use half-precision, the T400 provides a path to higher throughput per FLOP.

Q: How does memory bandwidth compare between the two?

A: The K40c has a massive advantage, with 288.4 GB/s over a 384-bit bus. The T400 manages only 80.00 GB/s over a 64-bit bus, which is a 72.3% reduction. This makes the K40c far better for memory-bound tasks.

Q: Which card is more power-efficient?

A: The T400 is dramatically more efficient, with a 30 W TDP versus the K40c’s 245 W. The T400 also has no external power connectors and requires only a 200 W PSU, while the K40c needs a 550 W PSU and dual connectors.

Q: Can either card be used for video output?

A: No for the K40c, which has no display outputs. Yes for the T400, which has 3x mini-DisplayPort 1.4a. This makes the T400 suitable for workstation desktop use, while the K40c is strictly a compute accelerator.

Q: What is the difference in API support?

A: The T400 supports DirectX 12 (12_1) and Vulkan 1.4, while the K40c supports DirectX 12 (11_0) and Vulkan 1.2.175. Both support OpenGL 4.6. The T400 also has a Geekbench Vulkan score of 15,976, whereas the K40c has no recorded Vulkan result.

Specification Differences

| Specification | NVIDIA Tesla K40c | NVIDIA T400 |

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

| Architecture | Kepler | Turing |

| Process Node | 28 nm | 12 nm |

| Transistors | 7,080 million | 4,700 million |

| Die Size | 561 mm² | 200 mm² |

| Transistor Density | 12.6M / mm² | 23.5M / mm² |

| Base Clock | 745 MHz | 420 MHz |

| Boost Clock | 876 MHz | 1,425 MHz |

| Memory Clock | 1502 MHz (6 Gbps effective) | 1250 MHz (10 Gbps effective) |

| Memory Size | 12 GB | 2 GB |

| Memory Type | GDDR5 | GDDR6 |

| Memory Bus Width | 384 bit | 64 bit |

| Memory Bandwidth | 288.4 GB/s | 80.00 GB/s |

| Shading Units | 2,880 | 384 |

| TMUs | 240 | 24 |

| ROPs | 48 | 16 |

| Pixel Rate | 52.56 GPixel/s | 22.80 GPixel/s |

| Texture Rate | 210.2 GTexel/s | 34.20 GTexel/s |

| FP32 Performance | 5.046 TFLOPS | 1,094.4 GFLOPS |

| FP16 Performance | N/A | 2.189 TFLOPS (2:1) |

| TDP | 245 W | 30 W |

| Slot Width | Dual-slot | Single-slot |

| Power Connectors | 1x 6-pin + 1x 8-pin | None |

| Suggested PSU | 550 W | 200 W |

| Display Outputs | No outputs | 3x mini-DisplayPort 1.4a |

| DirectX Support | 12 (11_0) | 12 (12_1) |

| Vulkan Support | 1.2.175 | 1.4 |

| Release Date | 2013-10-07 | 2021-05-05 |

| Launch MSRP | 7,699 USD | N/A |

| Generation | Tesla Kepler (Kxx) | Quadro Turing (Tx000) |

| Predecessor | Tesla Fermi | Quadro Volta |

| Successor | Tesla Maxwell | Workstation Ampere |