NVIDIA Tesla K40c vs NVIDIA Tesla M4 Comparison

The NVIDIA Tesla K40c and NVIDIA Tesla M4 are both end-of-life server accelerators from NVIDIA, but they target very different points in the Tesla lineup. Based on the single available benchmark, the Geekbench OpenCL score, the K40c holds a decisive edge over the M4, though the M4 counters with a vastly superior efficiency profile. The data shows a clear trade-off: raw compute throughput versus power consumption and architectural modernity.

Head-to-Head Benchmarks

The only direct comparison available is the Geekbench OpenCL test, and the result is a narrow but definitive win for the Tesla K40c. The K40c scores 17,468 points, while the Tesla M4 scores 16,932 points, giving the K40c a 3.2% advantage. This is a slim margin in raw performance terms, but it is consistent with the rest of the data pack.

Digging into the specifications, the performance gap is smaller than the hardware differences would suggest. The K40c offers 5.046 TFLOPS of FP32 compute, more than double the M4's 2.195 TFLOPS. Yet in the actual benchmark, the K40c only leads by 3.2%. This indicates that the Geekbench OpenCL workload does not scale linearly with theoretical compute, or that the M4's newer Maxwell architecture is more efficient at executing the specific instructions involved.

The K40c's wins are not limited to the score itself. It also commands a substantial lead in memory bandwidth, with 288.4 GB/s versus the M4's 88.00 GB/s — a 227% advantage. This memory bandwidth disparity is likely a major factor in the K40c's benchmark victory, as OpenCL workloads often stress memory throughput heavily. The K40c also has a 12 GB frame buffer versus the M4's 4 GB, allowing it to handle larger datasets without swapping.

However, the M4 does not go down without a fight. While it loses the raw performance race, it wins decisively on efficiency. The M4 draws just 50 W of power, compared to the K40c's 245 W — a fivefold reduction. This means the M4 delivers 16,932 points at 50 W, while the K40c delivers 17,468 points at 245 W. In terms of performance per watt, the M4 is the clear superior, offering roughly 338 points per watt versus the K40c's 71 points per watt.

The clock speeds tell a similar story. The M4 has a base clock of 872 MHz and a boost clock of 1072 MHz, while the K40c runs at 745 MHz base and 876 MHz boost. The M4 is therefore clocked 17% higher at base and 22% higher at boost, which helps it close the gap in actual application performance despite having far fewer shaders.

The Verdict

The data supports a split verdict depending on the use case. For pure compute performance, the NVIDIA Tesla K40c is the winner. Its 3.2% higher Geekbench OpenCL score, combined with its massive memory bandwidth and capacity advantages, makes it the better choice for workloads that are not power-constrained. The K40c also holds a higher percentile ranking at 61 versus the M4's 60, indicating it sits slightly higher in the overall GPU performance distribution.

However, for deployments where power consumption is a critical factor, the Tesla M4 is the logical pick. Its 50 W TDP is a fraction of the K40c's 245 W, and it requires a suggested PSU of just 250 W versus 550 W for the K40c. This makes the M4 far easier to integrate into dense server configurations with limited power budgets. The M4 also offers a more modern feature set, with DirectX 12 (12_1) support and Vulkan 1.4, whereas the K40c is limited to DirectX 12 (11_0) and Vulkan 1.2.175.

The K40c's launch MSRP was 7,699 USD, but since the M4 has no launch MSRP listed, a direct price comparison is not possible. The choice ultimately comes down to whether raw performance or efficiency is the higher priority.

Architecture Differences

The two cards are built on fundamentally different architectures. The Tesla K40c uses the GK180 chip, based on the Kepler architecture, which was introduced in the Tesla Kepler generation (Kxx). The Tesla M4 uses the GM206 chip, based on Maxwell 2.0, from the Tesla Maxwell generation (Mxx). This is a generational leap, with the M4 being the newer design.

The transistor counts reflect this architectural shift. The K40c packs 7,080 million transistors into a 561 mm² die, while the M4 manages 2,940 million transistors in a 228 mm² die. Interestingly, the transistor density is nearly identical: the K40c has 12.6 million transistors per mm², and the M4 has 12.9 million per mm². Both are fabricated on the same 28 nm process at TSMC, so the density difference is negligible.

The core configurations differ dramatically. The K40c has 2,880 shading units, 240 texture mapping units (TMUs), and 48 render output units (ROPs). The M4 has only 1,024 shading units, 64 TMUs, and 32 ROPs. This means the K40c has 181% more shaders and 275% more TMUs. Neither card features ray tracing cores or tensor cores, as both predate those technologies.

The memory subsystems are also architecturally distinct. The K40c uses a 384-bit memory bus with 12 GB of GDDR5, while the M4 uses a 128-bit bus with 4 GB of GDDR5. The K40c's memory runs at 1502 MHz (6 Gbps effective), while the M4's runs at 1375 MHz (5.5 Gbps effective). The wider bus and faster memory give the K40c a 3.27x bandwidth advantage.

The M4 does have one architectural advantage in API support. It supports DirectX 12 (12_1), while the K40c only supports DirectX 12 (11_0). Both cards support OpenGL 4.6, but the M4 also supports Vulkan 1.4, which is a more recent API version than the K40c's Vulkan 1.2.175.

Specification Differences

The following table highlights the key specification differences between the two cards:

| Specification | NVIDIA Tesla K40c | NVIDIA Tesla M4 |

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

| Chip | GK180 | GM206 |

| Architecture | Kepler | Maxwell 2.0 |

| Transistors | 7,080 million | 2,940 million |

| Die Size | 561 mm² | 228 mm² |

| Base Clock | 745 MHz | 872 MHz |

| Boost Clock | 876 MHz | 1072 MHz |

| Memory Size | 12 GB | 4 GB |

| Memory Bus | 384 bit | 128 bit |

| Memory Bandwidth | 288.4 GB/s | 88.00 GB/s |

| Shading Units | 2880 | 1024 |

| TMUs | 240 | 64 |

| ROPs | 48 | 32 |

| FP32 Compute | 5.046 TFLOPS | 2.195 TFLOPS |

| Pixel Rate | 52.56 GPixel/s | 34.30 GPixel/s |

| Texture Rate | 210.2 GTexel/s | 68.61 GTexel/s |

| TDP | 245 W | 50 W |

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

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

| Suggested PSU | 550 W | 250 W |

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

| Vulkan Support | 1.2.175 | 1.4 |

| Release Date | 2013-10-07 | 2015-11-09 |

| Predecessor | Tesla Fermi | Tesla Kepler |

| Successor | Tesla Maxwell | Tesla Pascal |

FAQ

Q: Which card is faster in Geekbench OpenCL?

A: The NVIDIA Tesla K40c is faster, scoring 17,468 points versus the Tesla M4's 16,932 points, a 3.2% difference.

Q: What is the power consumption difference?

A: The Tesla M4 draws only 50 W, while the Tesla K40c draws 245 W. This makes the M4 five times more power-efficient.

Q: How much memory does each card have?

A: The K40c has 12 GB of GDDR5 memory, while the M4 has 4 GB of GDDR5. The K40c also has a much wider 384-bit memory bus versus the M4's 128-bit bus.

Q: Do these cards support ray tracing?

A: No, neither the K40c nor the M4 has ray tracing cores or tensor cores. They are both older-generation compute accelerators.

Q: Which card has better API support?

A: The Tesla M4 has better API support, with DirectX 12 (12_1) and Vulkan 1.4, while the K40c supports DirectX 12 (11_0) and Vulkan 1.2.175.

Q: What are the physical dimensions of the cards?

A: The K40c is a dual-slot card measuring 267 mm in length, while the M4 is a single-slot card with no listed dimensions.

Where Each One Wins

The NVIDIA Tesla K40c wins in scenarios demanding maximum compute throughput. Its 5.046 TFLOPS of FP32 performance and 288.4 GB/s of memory bandwidth make it the stronger choice for data-heavy compute tasks. The 12 GB frame buffer allows it to process larger models or datasets without running out of memory. The K40c also wins in the benchmark, with a 3.2% higher Geekbench OpenCL score. Its higher pixel rate (52.56 GPixel/s versus 34.30 GPixel/s) and texture rate (210.2 GTexel/s versus 68.61 GTexel/s) further underscore its raw performance superiority.

The NVIDIA Tesla M4 wins in efficiency and deployment flexibility. Its 50 W TDP is a fraction of the K40c's 245 W, and it requires no external power connectors, whereas the K40c needs a 6-pin and an 8-pin connector. The M4's single-slot design makes it much easier to install in dense, multi-GPU servers, and its 250 W suggested PSU requirement means it can run in systems with far less headroom. The M4 also wins on architectural modernity, with support for DirectX 12 (12_1) and Vulkan 1.4, making it more future-proof for software that leverages these newer APIs.

For workloads that are memory-bound and require large datasets, the K40c is the clear winner. For workloads that are power-bound or need to fit into tight thermal envelopes, the M4 is the superior option. The benchmark data shows the K40c is 3.2% faster, but the M4 offers that performance at a fifth of the power draw, making it the pragmatic choice for scale-out deployments where efficiency is paramount.