AMD Radeon R6 M255DX vs NVIDIA GeForce 840M Comparison

# FAQ

Q: How do the NVIDIA GeForce 840M and AMD Radeon R6 M255DX compare in overall benchmark scores?

A: The NVIDIA GeForce 840M has an average benchmark score of 5322, while the AMD Radeon R6 M255DX scores 4867. This places the 840M about 9.3% higher in the database's aggregate measurements.

Q: Which GPU ranks higher in the overall percentile distribution?

A: The GeForce 840M sits at the 31st percentile among all GPUs, whereas the Radeon R6 M255DX is at the 28th percentile. The 840M outperforms roughly 3% more of the GPU landscape.

Q: What does the head-to-head Vulkan benchmark show?

A: In the only directly recorded head-to-head test, geekbench_vulkan, the 840M scores 4880 versus 4867 for the R6 M255DX, a 0.3% margin in favor of NVIDIA.

Q: Which GPU has the higher shading unit count?

A: The GeForce 840M has 384 shading units, while the Radeon R6 M255DX has 320, a difference of 64 units in NVIDIA's favor.

Q: What are the respective release dates?

A: The AMD Radeon R6 M255DX was released on January 6, 2014, and the NVIDIA GeForce 840M followed on March 11, 2014.

Q: Are both GPUs still in production?

A: No, both are marked as end-of-life in the database. The 840M lists the GeForce 700M as its predecessor and the GeForce 900M as its successor, while the R6 M255DX has no listed predecessor or successor.

Architecture Differences

The two GPUs come from different architectural lineages. The NVIDIA GeForce 840M is built on the Maxwell architecture, using the GM108S chip, and belongs to the GeForce 800M generation. The AMD Radeon R6 M255DX, by contrast, uses the GCN 1.0 architecture with the Jet chip, and is classified under the Gem System Hybrid (Rx M200) generation.

Both are fabricated by TSMC on a 28 nm process, but the transistor counts differ substantially. The 840M packs 1,020 million transistors on a 77 mm² die, yielding a transistor density of 13.2M per mm². The R6 M255DX contains 690 million transistors on a 56 mm² die, with a density of 12.3M per mm². The NVIDIA chip is therefore both larger in physical area and denser in transistor packing.

Clock behavior also separates the two. The 840M runs at a base clock of 1029 MHz with a boost of 1124 MHz, while the R6 M255DX operates at 780 MHz base and 855 MHz boost. This clock advantage contributes to the NVIDIA part's higher raw throughput figures.

Memory architecture is a fundamental divergence. The 840M has 2 GB of dedicated DDR3 memory on a 64-bit bus, delivering 16.02 GB/s of bandwidth with a memory clock of 1001 MHz (2 Gbps effective). The R6 M255DX uses system-shared memory entirely, with the type, bus width, and bandwidth all listed as system dependent. This means the AMD part relies on the host system's memory configuration, which can vary widely in practice.

Compute resources differ in composition. The 840M has 384 shading units, 16 texture mapping units (TMUs), and 8 render output units (ROPs). The R6 M255DX has 320 shading units, 20 TMUs, and 8 ROPs. Notably, AMD fields more TMUs despite having fewer shading units.

The resulting fill rates and compute throughput confirm NVIDIA's advantage. Pixel rate for the 840M is 8.992 GPixel/s versus 6.840 GPixel/s for the R6 M255DX. Texture rate is 17.98 GTexel/s versus 17.10 GTexel/s. FP32 compute comes to 863.2 GFLOPS for NVIDIA and 547.2 GFLOPS for AMD, a 316 GFLOPS gap.

Both GPUs support DirectX 12, but at different feature levels: the 840M at 11_0 and the R6 M255DX at 11_1. OpenGL support is identical at 4.6. Vulkan versions differ: the 840M supports 1.4, while the R6 M255DX supports 1.2.170.

The power profile shows the 840M at a 33 W TDP with no power connectors, while the R6 M255DX has no TDP listed in the database. Both are integrated-class parts (IGP slot width) with portable-device-dependent display outputs. The 840M uses a PCIe 3.0 x8 bus interface, whereas the R6 M255DX is listed simply as IGP.

Head-to-Head Benchmarks

The recorded data includes one direct comparison: geekbench_vulkan. In this test, the NVIDIA GeForce 840M scores 4880 against 4867 for the AMD Radeon R6 M255DX, producing a 0.3% delta in NVIDIA's favor. This is a narrow margin, well within what might be considered run-to-run variance for a single benchmark, but it does give the 840M a clean sweep of the head-to-head results with one win and zero losses.

Looking at the broader benchmark landscape, the 840M's average score of 5322 places it among a tight cluster of rivals. Its nearest competitors include the NVIDIA GeForce 930A at 5317 (0.1% behind), the NVIDIA GeForce GTX 980M at 5308 (0.3% behind), and the NVIDIA GeForce 940M at 5284 (0.7% behind). On the other side, the AMD Radeon R7 M445 scores 5358, which is 0.7% ahead of the 840M. This grouping shows the 840M sitting in a very competitive mid-range band where performance differences are minimal.

The R6 M255DX's average score of 4867 places it near a different set of rivals. The NVIDIA GeForce GTX 560M scores 4855 (0.2% behind), the NVIDIA GeForce 940MX scores 4844 (0.5% behind), and the NVIDIA GeForce GTS 450 scores 4893 (0.5% ahead). The NVIDIA GeForce RTX 5060 Ti 8 GB appears in this list at 4901, which is 0.7% ahead of the R6 M255DX, an odd pairing that likely reflects the database's percentile-based nearest-neighbor grouping rather than any practical comparison.

The gap between the two GPUs in average score is 455 points, which translates to roughly 9.3% of the R6 M255DX's score. While the head-to-head Vulkan result shows only a 0.3% difference, the average benchmark data suggests a more pronounced overall advantage for the 840M, likely because the aggregate includes additional workloads where the NVIDIA part's dedicated memory and higher clocks yield larger gains.

The Verdict

Based strictly on the recorded data, the NVIDIA GeForce 840M is the stronger performer. It wins the only head-to-head benchmark, holds a higher average score (5322 versus 4867), and sits at a higher percentile rank (31st versus 28th). Its advantage in FP32 compute (863.2 GFLOPS versus 547.2 GFLOPS) and pixel throughput (8.992 GPixel/s versus 6.840 GPixel/s) further supports this conclusion.

The R6 M255DX does have some structural advantages. Its 20 TMUs exceed the 840M's 16, which could benefit texture-heavy workloads in certain scenarios, and its DirectX 12 feature level of 11_1 is slightly higher than the 840M's 11_0. However, these advantages do not translate into a benchmark win in the available data.

For users choosing between these two end-of-life mobile GPUs, the 840M is the safer pick for general performance. The R6 M255DX's system-shared memory makes its real-world behavior heavily dependent on the host laptop's memory configuration, which introduces variability that the 840M's dedicated 2 GB DDR3 avoids. The 840M's higher clocks and larger shading unit count give it a clear edge in compute-bound workloads.

Specification Differences

The two GPUs differ in nearly every measurable specification:

• Chip: GM108S (NVIDIA) versus Jet (AMD)
• Architecture: Maxwell versus GCN 1.0
• Transistors: 1,020 million versus 690 million
• Die size: 77 mm² versus 56 mm²
• Transistor density: 13.2M / mm² versus 12.3M / mm²
• Base clock: 1029 MHz versus 780 MHz
• Boost clock: 1124 MHz versus 855 MHz
• Memory clock: 1001 MHz (2 Gbps effective) versus system shared
• Memory size: 2 GB DDR3 versus system shared
• Memory bus width: 64 bit versus system shared
• Memory bandwidth: 16.02 GB/s versus system dependent
• Shading units: 384 versus 320
• TMUs: 16 versus 20
• Pixel rate: 8.992 GPixel/s versus 6.840 GPixel/s
• Texture rate: 17.98 GTexel/s versus 17.10 GTexel/s
• FP32: 863.2 GFLOPS versus 547.2 GFLOPS
• TDP: 33 W versus not listed
• Bus interface: PCIe 3.0 x8 versus IGP
• DirectX support: 12 (11_0) versus 12 (11_1)
• Vulkan support: 1.4 versus 1.2.170
• Release date: March 11, 2014 versus January 6, 2014

Identical specifications include the 28 nm process node, TSMC foundry, 8 ROPs, IGP slot width, OpenGL 4.6 support, portable-device-dependent display outputs, and end-of-life production status.

Where Each One Wins

The NVIDIA GeForce 840M wins in raw compute throughput, with 863.2 GFLOPS FP32 performance that is 58% higher than the R6 M255DX's 547.2 GFLOPS. It also leads in pixel fill rate, texture fill rate, and benchmark scores. Its dedicated 2 GB DDR3 memory with 16.02 GB/s bandwidth provides predictable performance independent of system memory configuration. The 840M is the choice for applications that stress shading units, pixel throughput, and consistent memory bandwidth.

The AMD Radeon R6 M255DX wins in texture unit count, with 20 TMUs versus 16 on the 840M. This could provide a relative advantage in texture-bound workloads, though the 840M's higher texture rate (17.98 GTexel/s versus 17.10 GTexel/s) partially offsets this. The R6 M255DX also supports a slightly higher DirectX 12 feature level (11_1 versus 11_0), which may matter for specific API feature requirements. Its system-shared memory model could be beneficial in scenarios where the host system has ample fast memory, but this is highly dependent on the laptop's configuration.

For the majority of use cases, the 840M's higher clock speeds, greater shading unit count, and dedicated memory make it the superior option. The R6 M255DX's potential advantages are narrower and less impactful in the recorded benchmark data. Users with texture-heavy workloads might find the AMD part competitive, but the database measurements consistently favor NVIDIA.