NVIDIA Tesla K40c vs NVIDIA Tesla K80 Comparison

The NVIDIA Tesla K80 and NVIDIA Tesla K40c are both dual-slot, high-performance computing accelerators from the same Kepler family, but they are built around different chips and clock strategies. The K80 uses the GK210 chip while the K40c uses the GK180 chip, and this single difference cascades through their entire specification sheets. Both target the same compute workloads, but the data shows they achieve their performance in distinct ways, making the choice between them dependent on whether you prioritize raw throughput or power efficiency.

Architecture Differences

The K80 is based on the GK210 chip, which is a revision of the Kepler 2.0 architecture. The K40c, by contrast, uses the earlier GK180 chip and is labeled simply as "Kepler" rather than "Kepler 2.0." This architectural revision is not just a naming change; it reflects different design priorities. The GK210 in the K80 packs 7,100 million transistors on a 561 mm² die, while the GK180 in the K40c contains 7,080 million transistors on the identical 561 mm² die. The transistor density is nearly the same, at 12.7M / mm² for the K80 versus 12.6M / mm² for the K40c, indicating that the K80's extra transistors are used for different functional blocks rather than a denser layout.

The most telling architectural difference is in the compute unit counts versus clock speeds. The K40c's GK180 has more shading units (2880 versus 2496), more texture mapping units (240 versus 208), and the same 48 raster operation units. Despite having fewer cores, the K80 achieves its performance through a much higher effective clock strategy on a per-core basis? Actually, the opposite is true: the K40c has higher base and boost clocks (745 MHz and 876 MHz) compared to the K80 (562 MHz and 824 MHz). The K80 compensates for lower clocks and fewer cores by relying on the architectural improvements in GK210, which allows it to still win the single head-to-head benchmark available.

Both chips support DirectX 12, but with different feature levels: the K80 supports DirectX 12 (11_1) while the K40c supports DirectX 12 (11_0). OpenGL 4.6 and Vulkan 1.2.175 are identical on both. Neither card has any display outputs, reinforcing that these are pure compute accelerators. The memory subsystem is also identical in capacity and bus width, but the K40c runs its GDDR5 memory faster, as detailed below.

Specification Differences

The specification sheets differ in several key areas beyond the chip name. The most significant difference is in clock speeds: the K40c has a base clock of 745 MHz and a boost clock of 876 MHz, while the K80 operates at 562 MHz base and 824 MHz boost. This gives the K40c a substantial clock advantage. Memory clocks follow the same pattern: the K40c runs at 1502 MHz (6 Gbps effective) versus the K80's 1253 MHz (5 Gbps effective). Consequently, memory bandwidth is higher on the K40c at 288.4 GB/s versus 240.6 GB/s on the K80.

The shading unit count flips the advantage back to the K40c: 2880 versus 2496. Texture units are 240 versus 208, and ROPs are equal at 48. The K40c's higher clocks and more units translate into higher theoretical rates: pixel rate is 52.56 GPixel/s versus 42.85 GPixel/s, and texture rate is 210.2 GTexel/s versus 171.4 GTexel/s. FP32 compute is likewise higher on the K40c at 5.046 TFLOPS versus 4.113 TFLOPS on the K80. Neither card supports FP16, so that field is null on both.

Power and physical requirements differ. The K40c has a lower TDP of 245 W versus 300 W on the K80, and it requires a 550 W suggested PSU versus 700 W on the K80. Power connectors also differ: the K40c needs a 1x 6-pin + 1x 8-pin setup, while the K80 only requires 1x 8-pin. Both are dual-slot cards with identical dimensions of 267 mm (10.5 inches) in length and use PCIe 3.0 x16. The K40c has a launch MSRP of 7,699 USD. Both are end-of-life products, with the K40c released in October 2013 and the K80 in November 2014, and both share the same predecessor (Tesla Fermi) and successor (Tesla Maxwell).

Where Each One Wins

Based on the benchmark data, the K80 wins the only head-to-head test available, but the K40c wins on every theoretical specification. This creates a clear split: if you care about the numbers on paper, the K40c is superior in raw compute throughput, memory bandwidth, and clock speeds. If you care about actual benchmark results, the K80 delivers a higher score despite its lower specs. The K40c also wins on power efficiency, drawing 245 W versus 300 W, and requiring a smaller PSU. For workloads that are sensitive to memory bandwidth, the K40c's 288.4 GB/s gives it an edge. For workloads that respond to the architectural improvements in GK210, the K80's benchmark score suggests it handles real-world tasks more efficiently.

In terms of rival positioning, the K80 sits at the 63rd percentile of all GPUs with an average benchmark score of 18866. Its nearest rivals are the NVIDIA GeForce RTX 2070 (18789, deltaPct 0.4), the NVIDIA RTX 2000 Ada Generation (18954, deltaPct -0.5), the NVIDIA Quadro K6000 (19030, deltaPct -0.9), and the AMD Radeon RX 6600 (19036, deltaPct -0.9). The K40c is at the 61st percentile with an average score of 17468. Its nearest rivals are the AMD Radeon Pro 460 (17509, deltaPct -0.2), the AMD Radeon Pro 560 (17551, deltaPct -0.5), the AMD Radeon 780M (17588, deltaPct -0.7), and the NVIDIA GeForce RTX 4060 (17639, deltaPct -1). The K80 is effectively trading blows with modern consumer and workstation cards, while the K40c sits slightly below a cluster of newer, lower-power parts.

Head-to-Head Benchmarks

The only direct comparison available is the Geekbench OpenCL test. In this test, the K80 scores 18620 while the K40c scores 17468. The K80 wins with a delta of 6.6%. This is a meaningful margin, representing more than a thousand-point gap. The result is surprising given that the K40c has 384 more shading units, 32 more texture units, higher clocks on every axis, and 47.8 GB/s more memory bandwidth. The K80's architectural advantages in GK210 clearly outweigh the K40c's raw spec advantages in this compute workload.

The K80's OpenCL score of 18620 places it within 0.4% of the GeForce RTX 2070 (18789) and 0.5% below the RTX 2000 Ada Generation (18954). The K40c's score of 17468 is within 0.2% of the Radeon Pro 460 (17509) and 1% below the GeForce RTX 4060 (17639). This means that in OpenCL compute, the K80 performs like a modern mid-range consumer card, while the K40c performs like a low-end mobile or integrated part. The K80 also has a Geekbench Vulkan score of 19111, which is not directly comparable to the K40c since the K40c has no Vulkan benchmark listed. The K80's average benchmark score of 18866 versus the K40c's 17468 further confirms that the K80 is the faster card in practice.

FAQ

Q: Which card has more shading units?

A: The K40c has 2880 shading units, while the K80 has 2496. The K40c also has more texture units (240 versus 208), but both have the same 48 ROPs.

Q: How do their memory bandwidths compare?

A: The K40c offers 288.4 GB/s of bandwidth, which is higher than the K80's 240.6 GB/s. This is due to the K40c's faster memory clock of 1502 MHz (6 Gbps effective) versus 1253 MHz (5 Gbps effective) on the K80.

Q: Which card is more power-efficient?

A: The K40c has a lower TDP of 245 W compared to the K80's 300 W. The K40c also has a lower suggested PSU of 550 W versus 700 W for the K80.

Q: What are the DirectX feature level differences?

A: The K80 supports DirectX 12 (11_1), while the K40c supports DirectX 12 (11_0). Both support OpenGL 4.6 and Vulkan 1.2.175.

Q: Which card wins the available benchmark?

A: The K80 wins the Geekbench OpenCL test with a score of 18620 versus the K40c's 17468, a delta of 6.6%. The K80 also has a Vulkan score of 19111, while the K40c has no Vulkan benchmark listed.

Q: How do they rank against other GPUs?

A: The K80 is at the 63rd percentile of all GPUs with an average score of 18866, placing it near the GeForce RTX 2070. The K40c is at the 61st percentile with an average score of 17468, placing it near the Radeon Pro 460.

The Verdict

The data points to a clear, if counterintuitive, conclusion: the K80 is the faster card despite losing on every headline specification. The K80 wins the only head-to-head benchmark by a solid 6.6% margin, and its average benchmark score of 18866 is 8% higher than the K40c's 17468. The K80's percentile ranking of 63 versus the K40c's 61 reinforces this, and its nearest rivals include the GeForce RTX 2070 and RTX 2000 Ada Generation, while the K40c competes with the Radeon Pro 460 and Radeon 780M.

However, the K40c is not without merits. It offers higher theoretical FP32 performance (5.046 TFLOPS versus 4.113 TFLOPS), more memory bandwidth (288.4 GB/s versus 240.6 GB/s), and a significantly lower TDP (245 W versus 300 W). For compute workloads that are heavily bandwidth-bound or that scale with raw clock speed, the K40c's specifications suggest it could outperform the K80 in specific tasks, even though the general OpenCL benchmark favors the K80. The K40c also requires less power infrastructure, with a 550 W PSU recommendation versus 700 W.

For buyers choosing between these two end-of-life accelerators, the decision hinges on whether you trust benchmark results or theoretical specifications. The benchmark data shows the K80 is the better overall compute card, and it handles modern OpenCL and Vulkan workloads more effectively, as evidenced by its Vulkan score of 19111. The K40c is the better choice for power-constrained environments or for workloads that specifically benefit from its higher memory bandwidth and clock speeds. If you want the card that performs better in general compute, the K80 is the one to pick. If you need lower power draw and can exploit the K40c's higher theoretical throughput, it remains a viable option.