AMD Radeon HD 6850 X2 vs AMD Radeon R5 M420 Comparison

The AMD Radeon HD 6850 X2 and the AMD Radeon R5 M420 represent two distinct eras of AMD mobile and desktop graphics, yet their benchmark scores place them in near-identical performance territory. The data shows a single head-to-head comparison where the HD 6850 X2 edges out the R5 M420 by a razor-thin margin of 0.5%, scoring 3977 against 3956 in Geekbench OpenCL. This places both cards within the bottom quartile of all GPUs, with the HD 6850 X2 at the 24th percentile and the R5 M420 at the 23rd percentile. The closeness of their scores is remarkable given their fundamentally different architectures, memory configurations, and release timelines.

Head-to-Head Benchmarks

The only direct benchmark comparison available is Geekbench OpenCL, where the AMD Radeon HD 6850 X2 scores 3977 and the AMD Radeon R5 M420 scores 3956. This 0.5% delta translates to a 21-point difference, a margin that falls well within normal run-to-run variance for OpenCL workloads. The HD 6850 X2 wins the single head-to-head test, but the practical performance difference is negligible for most compute tasks.

Looking at the nearest rivals for each card provides additional context. The HD 6850 X2 sits just 0.3% ahead of the NVIDIA Quadro K2000 (3964) and 0.5% ahead of both the NVIDIA GeForce 830M (3957) and the R5 M420 itself. The R5 M420, meanwhile, is statistically tied with the GeForce 830M (0% delta) and trails the Quadro K2000 by 0.2%. In real-world terms, all four of these GPUs are clustered within a 1% performance band, making them functionally interchangeable for OpenCL compute workloads.

The benchmark data suggests that the architectural advantages of each card cancel out. The HD 6850 X2 brings significantly higher raw throughput metrics — 1.536 TFLOPS FP32 versus 544.0 GFLOPS for the R5 M420 — yet this nearly 3x theoretical advantage does not translate into a meaningful OpenCL score advantage. This discrepancy highlights how memory bandwidth, driver optimization, and workload characteristics can outweigh raw compute specifications in real benchmark scenarios.

Architecture Differences

The architectural gap between these two GPUs is substantial. The HD 6850 X2 uses the Barts chip built on TeraScale 2 architecture, manufactured on TSMC's 40 nm process. It packs 1,700 million transistors into a 255 mm² die, yielding a transistor density of 6.7 million transistors per square millimeter. The R5 M420, in contrast, uses the Jet chip based on GCN 1.0 architecture, built on a 28 nm process. It contains 690 million transistors on a much smaller 56 mm² die, achieving a higher density of 12.3 million transistors per square millimeter.

The memory subsystems represent one of the most striking differences. The HD 6850 X2 comes equipped with 2 GB of GDDR5 memory on a 256-bit bus, delivering 134.4 GB/s of bandwidth at 4.2 Gbps effective speed. The R5 M420 offers double the capacity at 4 GB, but uses DDR3 memory on a narrow 64-bit bus, resulting in just 16.00 GB/s of bandwidth at 2 Gbps effective. This represents an 8.4x bandwidth advantage for the HD 6850 X2, which likely explains why its higher compute throughput doesn't produce a larger benchmark lead — the R5 M420's lower bandwidth may be sufficient for the OpenCL workload tested, while other bottlenecks limit the HD 6850 X2.

Compute resource allocation differs dramatically. The HD 6850 X2 features 960 shading units, 48 texture mapping units, and 32 ROPs, producing a pixel rate of 25.60 GPixel/s and a texture rate of 38.40 GTexel/s. The R5 M420 is far more modest with 320 shading units, 20 TMUs, and just 8 ROPs, yielding 6.800 GPixel/s and 17.00 GTexel/s respectively. The HD 6850 X2 also carries a 254 W TDP and requires dual 8-pin power connectors with a 600 W suggested PSU, while the R5 M420 is an integrated graphics processor with no specified TDP or power connectors.

API support shows the generational shift. The R5 M420 supports DirectX 12 (11_1), OpenGL 4.6, and Vulkan 1.2.170, while the HD 6850 X2 is limited to DirectX 11.2 (11_0) and OpenGL 4.4 with no Vulkan support. The R5 M420 also uses PCIe 3.0 x8, whereas the HD 6850 X2 runs on PCIe 2.0 x16.

FAQ

Q: Which GPU has a higher OpenCL benchmark score?

A: The AMD Radeon HD 6850 X2 scores 3977 in Geekbench OpenCL, which is 0.5% higher than the AMD Radeon R5 M420's score of 3956. This represents a 21-point difference in the single head-to-head benchmark test.

Q: How do these cards compare to their closest competitors?

A: The HD 6850 X2 is 0.3% ahead of the NVIDIA Quadro K2000 and 0.5% ahead of the NVIDIA GeForce 830M. The R5 M420 is statistically tied with the GeForce 830M at 0% delta and trails the Quadro K2000 by 0.2%. All four GPUs sit within a 1% performance band.

Q: Which card has more memory bandwidth?

A: The HD 6850 X2 has 134.4 GB/s of bandwidth using GDDR5 memory on a 256-bit bus. The R5 M420 has only 16.00 GB/s using DDR3 on a 64-bit bus, representing an 8.4x bandwidth advantage for the HD 6850 X2.

Q: What are the power requirements for each card?

A: The HD 6850 X2 has a 254 W TDP, requires dual 8-pin power connectors, and suggests a 600 W PSU. The R5 M420 has no specified TDP, power connectors, or suggested PSU, as it is an integrated graphics processor.

Q: Which GPU supports newer graphics APIs?

A: The R5 M420 supports DirectX 12 (11_1), OpenGL 4.6, and Vulkan 1.2.170. The HD 6850 X2 is limited to DirectX 11.2 (11_0) and OpenGL 4.4, with no Vulkan support.

Q: How do physical specifications differ?

A: The HD 6850 X2 is a dual-slot card with 1,700 million transistors on a 255 mm² die using a 40 nm process. The R5 M420 is an IGP with 690 million transistors on a 56 mm² die using a 28 nm process, resulting in higher transistor density at 12.3M/mm² versus 6.7M/mm².

The Verdict

The data presents a clear case for a performance tie, but with vastly different underlying characteristics. The AMD Radeon HD 6850 X2 wins the only available benchmark by 0.5%, yet this margin is too small to constitute a meaningful performance advantage. Both cards occupy the 23rd-24th percentile of all GPUs, reinforcing their status as entry-level performers nearly a decade apart in release timing.

For users prioritizing compute performance in OpenCL workloads, the HD 6850 X2 holds a nominal edge, but its 254 W TDP and dual 8-pin power requirements make it a challenging component to integrate into modern systems. The R5 M420, as an integrated GPU with no discrete power requirements, offers the same practical performance in a far more energy-efficient package. Its support for DirectX 12, OpenGL 4.6, and Vulkan 1.2.170 also ensures broader software compatibility with modern applications.

The HD 6850 X2's massive bandwidth advantage (134.4 GB/s versus 16.00 GB/s) and 3x higher FP32 throughput (1.536 TFLOPS versus 544.0 GFLOPS) do not translate to benchmark dominance, suggesting the OpenCL test used is either memory-latency bound or limited by other factors. The R5 M420's smaller memory footprint per transaction, despite lower total bandwidth, appears sufficient for the tested workload.

From a pure specification standpoint, the HD 6850 X2 is the more capable hardware, but the R5 M420's architectural efficiency and modern API support make it the more practical choice for contemporary use. The benchmark data shows neither card offers a compelling advantage over the other, and both should be considered entry-level options for users with modest compute needs.

Specification Differences

| Specification | AMD Radeon HD 6850 X2 | AMD Radeon R5 M420 |

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

| Architecture | TeraScale 2 | GCN 1.0 |

| Generation | Northern Islands (HD 6800) | Gem System (R5 M400) |

| 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 | — | 780 MHz |

| Boost Clock | — | 850 MHz |

| Memory Clock | 1050 MHz / 4.2 Gbps effective | 1000 MHz / 2 Gbps effective |

| Memory Size | 2 GB | 4 GB |

| Memory Type | GDDR5 | DDR3 |

| Memory Bus Width | 256 bit | 64 bit |

| Memory Bandwidth | 134.4 GB/s | 16.00 GB/s |

| Shading Units | 960 | 320 |

| TMUs | 48 | 20 |

| ROPs | 32 | 8 |

| Pixel Rate | 25.60 GPixel/s | 6.800 GPixel/s |

| Texture Rate | 38.40 GTexel/s | 17.00 GTexel/s |

| FP32 | 1.536 TFLOPS | 544.0 GFLOPS |

| TDP | 254 W | — |

| Slot Width | Dual-slot | IGP |

| Power Connectors | 2x 8-pin | — |

| Suggested PSU | 600 W | — |

| Bus Interface | PCIe 2.0 x16 | PCIe 3.0 x8 |

| 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 | — | 1.2.170 |

| Release Date | 2011-09-18 | 2016-05-14 |

| Predecessor | Evergreen | Solar System |

| Successor | Southern Islands | Polaris Mobile |

| OpenCL Score | 3977 | 3956 |

| Percentile | 24 | 23 |