NVIDIA Tesla K20c vs NVIDIA Tesla K20Xm Comparison

The NVIDIA Tesla K20Xm and Tesla K20c are both dual-slot, end-of-life compute accelerators built on the GK110 chip and the Kepler architecture. They share the same 28 nm TSMC process node, 7,080 million transistors, and a 561 mm² die size, but the data reveals they are configured very differently. The K20Xm is the more potent part, with a 50% higher OpenCL benchmark score, while the K20c is a more modest variant with a lower launch MSRP. Both cards are designed for compute workloads, lacking any display outputs, and target the same Tesla Kepler generation.

FAQ

Q: Which GPU has the higher average benchmark score?

A: The NVIDIA Tesla K20Xm has an average benchmark score of 12,625, compared to the Tesla K20c's 11,479. This places the K20Xm in the 52nd percentile of all GPUs, while the K20c sits in the 51st percentile.

Q: How much faster is the K20Xm in the head-to-head OpenCL test?

A: In the geekbench_opencl test, the K20Xm scored 17,215 against the K20c's 11,479, a delta of 50%. This is the only head-to-head benchmark recorded, and it decisively favors the K20Xm.

Q: What are the memory specifications for each card?

A: The K20Xm has 6 GB of GDDR5 memory on a 384-bit bus, delivering 249.6 GB/s of bandwidth. The K20c has 5 GB of GDDR5 memory on a 320-bit bus, providing 208.0 GB/s of bandwidth. Both run at the same memory clock of 1300 MHz (5.2 Gbps effective).

Q: Do these cards have any display outputs?

A: No. Both the NVIDIA Tesla K20Xm and Tesla K20c are listed with "No outputs," indicating they are compute-only accelerators without video connectivity.

Q: What is the difference in the shading unit count?

A: The K20Xm contains 2,688 shading units, while the K20c has 2,496. This difference is reflected in the FP32 performance, where the K20Xm achieves 3.935 TFLOPS versus the K20c's 3.524 TFLOPS.

Q: What is the launch MSRP for each model?

A: The launch MSRP for the NVIDIA Tesla K20Xm is 7,699 USD. The launch MSRP for the NVIDIA Tesla K20c is 3,199 USD.

Where Each One Wins

The benchmark data shows a single point of comparison, but it is a clear one. The NVIDIA Tesla K20Xm wins the only head-to-head benchmark, geekbench_opencl, with a substantial 50% margin. This suggests the K20Xm is the superior choice for raw compute throughput in OpenCL workloads. Its higher shading unit count, wider memory bus, and larger memory pool all contribute to this outcome.

The NVIDIA Tesla K20c, however, does not win any benchmarks in this comparison. Its sole recorded benchmark score is the 11,479 in geekbench_opencl, which is lower than the K20Xm's score in the same test. While it has no direct wins, its lower TDP of 225 W (versus 235 W for the K20Xm) and lower launch MSRP might make it a more accessible option for certain deployment scenarios, though the data does not quantify these trade-offs in performance terms.

Architecture Differences

Both GPUs are built on the same foundational architecture, but their internal configurations diverge significantly. The K20Xm and K20c both use the GK110 chip and the Kepler architecture, fabricated at TSMC on a 28 nm process. The transistor count is identical at 7,080 million, and the die size is the same 561 mm². However, the K20Xm has a more fully enabled chip, with 2,688 shading units, 224 texture mapping units (TMUs), and 48 render output units (ROPs). The K20c is slightly cut down, featuring 2,496 shading units, 208 TMUs, and 40 ROPs.

The memory subsystem also differs. The K20Xm uses a 384-bit bus, allowing for a 6 GB frame buffer, while the K20c's 320-bit bus supports 5 GB. This results in a bandwidth advantage for the K20Xm (249.6 GB/s vs. 208.0 GB/s). The K20Xm also has a higher pixel rate (40.99 GPixel/s vs. 36.71 GPixel/s) and texture rate (164.0 GTexel/s vs. 146.8 GTexel/s), reflecting its additional processing resources. Both cards share the same API support, including DirectX 12 (11_0), OpenGL 4.6, and Vulkan 1.2.175, and neither features RT or Tensor cores.

Specification Differences

The key specification differences between the two cards are numerical and direct. The K20Xm has 6 GB of memory versus 5 GB on the K20c. The memory bus width is 384-bit on the K20Xm and 320-bit on the K20c. Consequently, the memory bandwidth is 249.6 GB/s for the K20Xm and 208.0 GB/s for the K20c. The shading unit count is 2,688 versus 2,496, and the TMU count is 224 versus 208. The ROP count is 48 on the K20Xm and 40 on the K20c.

Compute performance scales with these differences: FP32 is 3.935 TFLOPS on the K20Xm and 3.524 TFLOPS on the K20c. The pixel rate is 40.99 GPixel/s versus 36.71 GPixel/s, and the texture rate is 164.0 GTexel/s versus 146.8 GTexel/s. The TDP is slightly higher on the K20Xm at 235 W, compared to 225 W on the K20c. The bus interface also differs, with the K20Xm using PCIe 3.0 x16 and the K20c using PCIe 2.0 x16. The K20c has explicit power connectors listed (1x 6-pin + 1x 8-pin), while the K20Xm's are not specified. Both are dual-slot cards with a length of 267 mm (10.5 inches).

Head-to-Head Benchmarks

The only head-to-head benchmark available is geekbench_opencl, and it delivers a decisive result. The NVIDIA Tesla K20Xm scores 17,215, while the NVIDIA Tesla K20c scores 11,479. This represents a 50% delta in favor of the K20Xm. This is a massive gap, indicating a clear performance tier separation between the two cards.

Looking at the nearest rivals for each card provides more context. The K20Xm's average score of 12,625 places it near the AMD Radeon RX 7600M XT (12,710, -0.7%), the NVIDIA GeForce GTX 670 (12,773, -1.2%), and the NVIDIA GeForce GTX 590 (12,830, -1.6%). The K20c's average score of 11,479 is close to the AMD Radeon Pro 5500M (11,528, -0.4%), the AMD Radeon RX 7800 XT (11,627, -1.3%), and the NVIDIA GeForce GTX 1660 (11,680, -1.7%). Notably, the K20c is actually 1.9% ahead of the NVIDIA GeForce GTX 780M (11,261), one of its nearest rivals.

The data suggests that while both cards are in the same performance ballpark as their respective rivals, the K20Xm is significantly ahead of the K20c. The 50% delta in the head-to-head test is far larger than the single-digit percentage differences seen between each card and its nearest competitors. This implies that the K20Xm is not just a slightly better version of the K20c, but a fundamentally stronger compute part.

The Verdict

The data is unambiguous: the NVIDIA Tesla K20Xm is the superior performer. It wins the only head-to-head benchmark with a 50% margin, and its average benchmark score of 12,625 is nearly 10% higher than the K20c's 11,479. For any workload reliant on OpenCL compute, the K20Xm is the clear choice, delivering substantially higher FP32 throughput, memory bandwidth, and texture fill rates.

The NVIDIA Tesla K20c, while a capable compute card in its own right, is simply outclassed by the K20Xm. Its lower specifications across the board—fewer shading units, less memory, a narrower bus, and lower bandwidth—translate directly into the observed performance deficit. The K20c does have a lower TDP (225 W vs. 235 W) and a lower launch MSRP (3,199 USD vs. 7,699 USD), but the performance gap is so large that these advantages may not compensate for the loss in compute capability. Users should select the K20c only if the absolute performance of the K20Xm is not required and the lower power draw or initial cost is a primary constraint. For all other compute-intensive tasks, the K20Xm is the definitive pick based on the benchmark evidence.