AMD Radeon HD 6850 X2 vs AMD Radeon R6 M255DX Comparison

# AMD Radeon HD 6850 X2 vs AMD Radeon R6 M255DX

The AMD Radeon HD 6850 X2 and the AMD Radeon R6 M255DX target fundamentally different roles. The HD 6850 X2 is a dual-GPU desktop card from 2011, built for raw throughput in a power-hungry slot, while the R6 M255DX is an integrated graphics processor from 2014, designed for portability and efficiency. Benchmark data confirms this split: the HD 6850 X2 scores 3977 in Geekbench OpenCL, while the R6 M255DX scores 4867 in Geekbench Vulkan. These numbers come from different APIs, so they are not directly comparable, but they reveal distinct strengths. The HD 6850 X2 lands in the 24th percentile of all GPUs, while the R6 M255DX sits at the 28th percentile. Neither is a high-flying performer, but each excels in its own context.

Where Each One Wins

The HD 6850 X2 wins in raw compute throughput and legacy API performance. Its OpenCL score of 3977 places it 0.3% ahead of the NVIDIA Quadro K2000 (3964), 0.5% ahead of the NVIDIA GeForce 830M (3957), and 0.5% ahead of the AMD Radeon R5 M420 (3956). This is a narrow margin, but it shows the card holds its own against a generation of mobile and workstation parts. The dual-GPU design, with 960 shading units and a 256-bit memory bus, gives it a substantial advantage in fill-rate and texture work. Its pixel rate of 25.60 GPixel/s and texture rate of 38.40 GTexel/s are far beyond what the R6 M255DX can manage.

The R6 M255DX wins in modern API support and Vulkan performance. Its Vulkan score of 4867 places it 0.2% ahead of the NVIDIA GeForce GTX 560M (4855), 0.5% ahead of the NVIDIA GeForce 940MX (4844), and 0.7% behind the NVIDIA GeForce RTX 5060 Ti 8 GB (4901). This is a strong showing for an integrated part, and it indicates that the R6 M255DX handles modern workloads more gracefully than its older rival. The R6 M255DX also supports DirectX 12 (11_1), OpenGL 4.6, and Vulkan 1.2.170, while the HD 6850 X2 tops out at DirectX 11.2 (11_0) and OpenGL 4.4 with no Vulkan support. For any application that leverages Vulkan or DirectX 12, the R6 M255DX is the only viable option.

The use-case split is clear: the HD 6850 X2 suits legacy DirectX 11 workloads and compute-heavy tasks, while the R6 M255DX suits modern API-driven applications, particularly those that can exploit Vulkan. The HD 6850 X2 is a desktop card with a 600 W suggested PSU and dual-slot cooler, so it belongs in a tower with ample power. The R6 M255DX is an IGP, so it lives in a laptop or small-form-factor device where power draw and space are constrained.

Architecture Differences

The two GPUs come from different architectural eras. The HD 6850 X2 uses the Barts chip on TeraScale 2 architecture, belonging to the Northern Islands (HD 6800) generation. It is fabricated on a 40 nm process at TSMC, with 1,700 million transistors on a 255 mm² die. The transistor density is 6.7 million per mm². This is a mature, power-hungry design with a 254 W TDP, requiring two 8-pin power connectors.

The R6 M255DX uses the Jet chip on GCN 1.0 architecture, from the Gem System Hybrid (Rx M200) generation. It is fabricated on a 28 nm process at TSMC, with 690 million transistors on a 56 mm² die. The transistor density is 12.3 million per mm², nearly double that of the older chip. This density gain reflects the newer process node and architectural efficiency. The R6 M255DX has no separate TDP figure, as it is an IGP, and it uses system shared memory rather than dedicated VRAM.

Memory configurations differ drastically. The HD 6850 X2 has 2 GB of GDDR5 on a 256-bit bus, delivering 134.4 GB/s of bandwidth and a memory clock of 1050 MHz (4.2 Gbps effective). The R6 M255DX uses system shared memory, with a bus width that is system dependent and bandwidth that is also system dependent. This means the R6 M255DX's memory performance depends entirely on the host system's RAM and memory controller, which is a major disadvantage in bandwidth-sensitive tasks.

The HD 6850 X2 has 960 shading units, 48 TMUs, and 32 ROPs, while the R6 M255DX has 320 shading units, 20 TMUs, and 8 ROPs. The HD 6850 X2's FP32 throughput is 1.536 TFLOPS, while the R6 M255DX manages only 547.2 GFLOPS. The HD 6850 X2 supports PCIe 2.0 x16, while the R6 M255DX uses an IGP bus interface, meaning it communicates over the internal system bus rather than a PCIe slot.

Head-to-Head Benchmarks

There are no direct head-to-head benchmark results in the database, so the comparison relies on each card's individual benchmark scores and their nearest rivals. The HD 6850 X2's OpenCL score of 3977 puts it 0.3% ahead of the NVIDIA Quadro K2000 (3964), 0.5% ahead of the NVIDIA GeForce 830M (3957), and 0.5% ahead of the AMD Radeon R5 M420 (3956). These are tight margins, showing that the HD 6850 X2 is competitive with a range of mid-range mobile and workstation GPUs from a few years later.

The R6 M255DX's Vulkan score of 4867 puts it 0.2% ahead of the NVIDIA GeForce GTX 560M (4855), 0.5% ahead of the NVIDIA GeForce 940MX (4844), and 0.5% behind the NVIDIA GeForce GTS 450 (4893). The closest rival is actually the NVIDIA GeForce RTX 5060 Ti 8 GB at 4901, which is 0.7% ahead. This is notable: an integrated GPU from 2014 is within 1% of a modern discrete card in Vulkan performance. The data suggests that the R6 M255DX is well-optimized for the Vulkan API, likely due to its GCN architecture and driver support.

When comparing the two directly, the R6 M255DX has a higher raw score (4867 vs 3977), but this is not a fair comparison because they use different benchmark APIs. The HD 6850 X2 does not support Vulkan, so it cannot run the same test. Conversely, the R6 M255DX could run OpenCL, but no OpenCL score is recorded in the database for it. The only fair statement is that the HD 6850 X2 is strong in OpenCL while the R6 M255DX is strong in Vulkan. Neither card has a clear win in the other's domain.

The HD 6850 X2's pixel rate of 25.60 GPixel/s is 3.7 times higher than the R6 M255DX's 6.840 GPixel/s. Its texture rate of 38.40 GTexel/s is 2.2 times higher than the R6 M255DX's 17.10 GTexel/s. These are substantial differences in fixed-function throughput, which matter for traditional rasterization workloads. However, the R6 M255DX has a higher boost clock (855 MHz vs no boost clock listed for the HD 6850 X2), which helps it in latency-sensitive tasks.

FAQ

Q: Which GPU has a higher benchmark score?

A: The R6 M255DX scores 4867 in Geekbench Vulkan, while the HD 6850 X2 scores 3977 in Geekbench OpenCL. The scores come from different APIs, so they are not directly comparable.

Q: Does the HD 6850 X2 support Vulkan?

A: No. The HD 6850 X2 supports DirectX 11.2 (11_0) and OpenGL 4.4, with no Vulkan support listed. The R6 M255DX supports Vulkan 1.2.170.

Q: Which GPU has more shading units?

A: The HD 6850 X2 has 960 shading units, while the R6 M255DX has 320 shading units. The HD 6850 X2 also has 48 TMUs and 32 ROPs, compared to 20 TMUs and 8 ROPs for the R6 M255DX.

Q: How does the memory configuration differ?

A: The HD 6850 X2 has 2 GB of GDDR5 on a 256-bit bus with 134.4 GB/s bandwidth. The R6 M255DX uses system shared memory, with bus width and bandwidth dependent on the host system.

Q: What is the transistor count difference?

A: The HD 6850 X2 has 1,700 million transistors on a 255 mm² die, while the R6 M255DX has 690 million transistors on a 56 mm² die. The R6 M255DX has a higher transistor density at 12.3M per mm² versus 6.7M per mm².

Q: Which GPU has a higher FP32 throughput?

A: The HD 6850 X2 has 1.536 TFLOPS of FP32 performance, while the R6 M255DX has 547.2 GFLOPS. The HD 6850 X2 is nearly three times faster in raw floating-point compute.

Specification Differences

| Specification | AMD Radeon HD 6850 X2 | AMD Radeon R6 M255DX |

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

| Architecture | TeraScale 2 | GCN 1.0 |

| Generation | Northern Islands (HD 6800) | Gem System Hybrid (Rx M200) |

| Process Node | 40 nm | 28 nm |

| Transistors | 1,700 million | 690 million |

| Die Size | 255 mm² | 56 mm² |

| Transistor Density | 6.7M / mm² | 12.3M / mm² |

| Base Clock | Not listed | 780 MHz |

| Boost Clock | Not listed | 855 MHz |

| Memory Clock | 1050 MHz (4.2 Gbps effective) | System Shared |

| Memory Size | 2 GB | System Shared |

| Memory Type | GDDR5 | System Shared |

| Memory Bus Width | 256 bit | System Shared |

| Memory Bandwidth | 134.4 GB/s | System Dependent |

| Shading Units | 960 | 320 |

| TMUs | 48 | 20 |

| ROPs | 32 | 8 |

| Pixel Rate | 25.60 GPixel/s | 6.840 GPixel/s |

| Texture Rate | 38.40 GTexel/s | 17.10 GTexel/s |

| FP32 | 1.536 TFLOPS | 547.2 GFLOPS |

| TDP | 254 W | Not listed |

| Slot Width | Dual-slot | IGP |

| Power Connectors | 2x 8-pin | None |

| Suggested PSU | 600 W | Not listed |

| Bus Interface | PCIe 2.0 x16 | IGP |

| Display Outputs | 2x DVI, 1x HDMI 1.3a, 1x DisplayPort 1.1 | Portable Device Dependent |

| DirectX | 11.2 (11_0) | 12 (11_1) |

| OpenGL | 4.4 | 4.6 |

| Vulkan | Not listed | 1.2.170 |

| Release Date | 2011-09-18 | 2014-01-06 |

The Verdict

The data points to a clear division of roles. The AMD Radeon HD 6850 X2 is the choice for anyone running legacy DirectX 11 applications or compute workloads that rely on OpenCL. Its 1.536 TFLOPS of FP32 power, 134.4 GB/s of memory bandwidth, and 38.40 GTexel/s texture rate make it a capable part for its era. It sits just 0.3% ahead of the NVIDIA Quadro K2000 and 0.5% ahead of the GeForce 830M in OpenCL, showing it remains competitive against later mid-range parts. However, it requires a 600 W PSU and a dual-slot motherboard, and its 254 W TDP means it is not suitable for compact or power-sensitive systems.

The AMD Radeon R6 M255DX is the choice for anyone who needs modern API support and is working within a portable or integrated form factor. Its Vulkan score of 4867 is 0.2% ahead of the GeForce GTX 560M and 0.5% ahead of the GeForce 940MX, which is impressive for an IGP. It supports DirectX 12, OpenGL 4.6, and Vulkan 1.2.170, making it far more future-proof in terms of software compatibility. Its 28 nm process and 12.3M / mm² transistor density show a more efficient design, and its lack of discrete power connectors makes it drop-in for laptops and small devices.

The verdict depends entirely on the use case. For a desktop system with ample power and a focus on older DirectX titles or OpenCL compute, the HD 6850 X2 is the stronger option. For a mobile or compact system that needs to run Vulkan-based applications or DirectX 12 games, the R6 M255DX is the only sensible pick. The HD 6850 X2 wins on raw throughput and memory bandwidth, while the R6 M255DX wins on API support and efficiency. Neither card is a dominant performer, but each serves its intended niche effectively. The recorded data shows no head-to-head benchmark results, so any direct comparison must account for the different APIs used in their respective tests.