AMD Radeon HD 6850 X2 vs NVIDIA Quadro P400 Comparison

Head-to-Head Benchmarks

The only directly comparable benchmark in the database is Geekbench OpenCL, and the NVIDIA Quadro P400 takes it with a score of 4,249 against the AMD Radeon HD 6850 X2’s 3,977. That is a 6.8% delta, a clear but not overwhelming win for the newer card. In practical terms, the Quadro P400 is about seven percent ahead in raw compute workloads that scale well across shading units, which is modest given the age gap between the two designs.

Looking at the broader database context, the Quadro P400’s average benchmark score sits at 4,684, placing it in the 27th percentile of all GPUs. Its nearest rivals include the AMD Radeon RX 9060 XT 16 GB and AMD Radeon R5 M320, both with an average score of 4,657, meaning the P400 is 0.6% ahead of them. The NVIDIA GeForce GTX 970M trails slightly with a 4,628 average, putting the P400 1.2% ahead. Meanwhile, the AMD Radeon R8 M445DX scores 4,727, which is 0.9% higher than the P400, so the Quadro is effectively trading blows with those midrange parts.

The HD 6850 X2, by contrast, has an average benchmark score of 3,977, placing it in the 24th percentile. Its nearest rivals are the NVIDIA Quadro K2000 (3,964, just 0.3% behind), the NVIDIA GeForce 830M (3,957, 0.5% behind), and the AMD Radeon R5 M420 (3,956, 0.5% behind). The HD 6850 X2 also edges out the NVIDIA GeForce GT 745M (3,953) by 0.6%. This shows the HD 6850 X2 is grouped with entry-level mobile and older workstation parts, whereas the P400 is grouped with more capable mobile GPUs and a modern midrange card.

The single head-to-head result also masks the architectural gulf between them. The P400 wins the only measured test, but the HD 6850 X2 has significantly higher theoretical throughput in several metrics. In FP32 compute, the HD 6850 X2 delivers 1.536 TFLOPS versus the P400’s 641.0 GFLOPS, meaning the older AMD card has about 2.4 times the raw single-precision compute. Yet the OpenCL score tells a different story: the P400 wins by 6.8%, indicating that the HD 6850 X2’s extra shading units (960 versus 256) do not translate into effective compute in this workload. The P400’s higher clock efficiency and newer architecture compensate for the massive unit count deficit.

Architecture Differences

The two GPUs are separated by two generations of design philosophy. The NVIDIA Quadro P400 uses the GP107 chip built on a 14 nm process at Samsung, packing 3,300 million transistors into a 132 mm² die. That yields a transistor density of 25.0 million per square millimeter. The architecture is Pascal, a design focused on efficiency and compute per watt. It supports DirectX 12 (12_1), OpenGL 4.6, and Vulkan 1.4.

The AMD Radeon HD 6850 X2 is based on the Barts chip, built on a 40 nm process at TSMC. It contains 1,700 million transistors on a 255 mm² die, giving a transistor density of just 6.7 million per square millimeter. The architecture is TeraScale 2, a much older design that lacks hardware support for modern APIs. It supports DirectX 11.2 (11_0) and OpenGL 4.4, but has no Vulkan support at all. The process node difference alone explains a lot: the P400 uses a process that is over twice as dense, allowing more transistors in a smaller die while consuming far less power.

Memory configurations also differ sharply. The P400 uses 2 GB of GDDR5 on a 64-bit bus, achieving 32.06 GB/s of bandwidth. The HD 6850 X2 also has 2 GB of GDDR5, but on a 256-bit bus, delivering 134.4 GB/s. That is over four times the memory bandwidth for the AMD card. In theory, that should give the HD 6850 X2 a big advantage in bandwidth-bound tasks, but the benchmark data shows the P400 still wins OpenCL, suggesting the architecture is more efficient at using its narrower bus.

The shading engine is a stark contrast. The P400 has 256 shading units, 16 TMUs, and 16 ROPs. The HD 6850 X2 has 960 shading units, 48 TMUs, and 32 ROPs. The AMD card has nearly four times the shading units, three times the TMUs, and double the ROPs. Yet the P400 still edges it out in the recorded benchmark. The P400’s pixel rate is 20.03 GPixel/s and texture rate is 20.03 GTexel/s, while the HD 6850 X2 achieves 25.60 GPixel/s and 38.40 GTexel/s, respectively. So the AMD card is faster in raw rasterization and texturing, but that does not translate into a higher OpenCL score.

FAQ

Q: Which GPU is faster in Geekbench OpenCL?

A: The NVIDIA Quadro P400 scores 4,249, which is 6.8% higher than the AMD Radeon HD 6850 X2’s 3,977.

Q: Does the AMD Radeon HD 6850 X2 support Vulkan?

A: No, the HD 6850 X2 has no Vulkan support. The Quadro P400 supports Vulkan 1.4.

Q: How much memory bandwidth does each card have?

A: The Quadro P400 has 32.06 GB/s, while the HD 6850 X2 has 134.4 GB/s, giving the AMD card a large advantage in that metric.

Q: What is the power draw difference?

A: The Quadro P400 has a TDP of 30 W, while the HD 6850 X2 is rated at 254 W. The P400 is a single-slot card with no power connectors and suggests a 200 W PSU, while the HD 6850 X2 is dual-slot, requires two 8-pin connectors, and suggests a 600 W PSU.

Q: Which GPU has more shading units?

A: The HD 6850 X2 has 960 shading units, while the Quadro P400 has 256, but the P400 still wins the recorded OpenCL benchmark.

Q: What is the release date difference?

A: The Quadro P400 was released on February 6, 2017, while the HD 6850 X2 was released on September 18, 2011.

Specification Differences

The two cards diverge in nearly every core specification except memory size (both 2 GB) and memory type (both GDDR5). The process node is 14 nm for the P400 versus 40 nm for the HD 6850 X2. Transistor count is 3,300 million versus 1,700 million, and die size is 132 mm² versus 255 mm². Transistor density is 25.0 million per mm² versus 6.7 million per mm².

The base and boost clocks on the HD 6850 X2 are not listed, but the P400 has a base clock of 1228 MHz and a boost of 1252 MHz. Memory clock is 1002 MHz (4 Gbps effective) for the P400 and 1050 MHz (4.2 Gbps effective) for the HD 6850 X2. The memory bus width is 64 bit versus 256 bit, and bandwidth is 32.06 GB/s versus 134.4 GB/s.

Shading units are 256 versus 960, TMUs are 16 versus 48, and ROPs are 16 versus 32. Pixel rate is 20.03 GPixel/s versus 25.60 GPixel/s, texture rate is 20.03 GTexel/s versus 28.40 GTexel/s, and FP32 is 641.0 GFLOPS versus 1.536 TFLOPS. The P400 has FP16 performance of 10.02 GFLOPS (1:64 ratio), while the HD 6850 X2 has no FP16 listing.

TDP is 30 W versus 254 W. The P400 is single-slot with no power connectors and a suggested PSU of 200 W, while the HD 6850 X2 is dual-slot with two 8-pin connectors and a suggested PSU of 600 W. The bus interface is PCIe 3.0 x16 versus PCIe 2.0 x16. Display outputs are 3x mini-DisplayPort 1.4a versus 2x DVI, 1x HDMI 1.3a, and 1x DisplayPort 1.1. The P400 supports DirectX 12 (12_1), OpenGL 4.6, and Vulkan 1.4, while the HD 6850 X2 supports DirectX 11.2 (11_0) and OpenGL 4.4, with no Vulkan.

The HD 6850 X2 has no listed dimensions, while the P400 is 150 mm long and 69 mm tall.

Where Each One Wins

The Quadro P400 wins in efficiency and modern feature support. Its 30 W TDP and no power connectors make it a drop-in card for any system with a 200 W PSU, and its single-slot design fits in tight chassis. It supports Vulkan, DirectX 12 (12_1), and DisplayPort 1.4a, which are essential for modern compute and display workloads. In the only direct benchmark, it beats the HD 6850 X2 by 6.8% in OpenCL.

The HD 6850 X2 wins in raw bandwidth and compute hardware. Its 256-bit bus and 134.4 GB/s bandwidth dwarf the P400’s 64-bit bus and 32.06 GB/s. It has three times the shading units, three times the TMUs, and double the ROPs. Its FP32 of 1.536 TFLOPS is more than double the P400’s 641.0 GFLOPS. Its pixel rate and texture rate are also higher: 25.60 GPixel/s and 38.40 GTexel/s versus 20.03 and 20.03, respectively. So if a workload is purely bound by memory bandwidth or raw pixel/texture throughput, the HD 6850 X2 has a theoretical edge.

The P400 also sits in a higher percentile ranking (27th versus 24th) and has a higher average benchmark score (4,684 versus 3,977). The HD 6850 X2’s nearest rivals are all older or low-end parts, while the P400 is matched with midrange cards like the Radeon RX 9060 XT and the GTX 970M.

The Verdict

The data points to one clear choice for most users: the NVIDIA Quadro P400. It wins the only head-to-head benchmark, has a higher average score, sits in a higher percentile, and does so at a fraction of the power draw (30 W versus 254 W). Its modern features, such as Vulkan 1.4, DisplayPort 1.4a, and PCIe 3.0, make it a more relevant card for today’s software stack. The HD 6850 X2, despite having three times the shading units and four times the memory bandwidth, cannot convert that hardware advantage into a benchmark win, and its lack of Vulkan and older DirectX support severely limits its use in modern workloads.

For users who need raw memory bandwidth and pixel throughput, the HD 6850 X2 might have a niche, but those numbers do not materialize into a measured win. The P400 is the better all-rounder for compute tasks, and the efficiency gap is enormous, with the HD 6850 X2 requiring a 600 W PSU and two 8-pin connectors, which is a major system requirement. The data is clear: the P400 is the card to pick for any new build, while the HD 6850 X2 is a historical artifact with theoretical strengths that never appear in practice.

The verdict is straightforward. Choose the Quadro P400 for modern compatibility, efficiency, and better benchmark performance. The HD 6850 X2 can only be recommended for legacy systems where its high bandwidth is usable and its power draw is not a concern, but that scenario does not apply to any current workload.