AMD Radeon R5 M255 vs AMD Radeon R8 M445DX Comparison

Head-to-Head Benchmarks

The direct comparison between these two mobile GPUs is limited to a single OpenCL benchmark result. In the Geekbench OpenCL test, the AMD Radeon R8 M445DX scores 4727, while the AMD Radeon R5 M255 scores 4650. This gives the R8 M445DX a 1.6% advantage, a narrow margin that places both parts in the same performance tier. The data shows a win for the R8 M445DX, though the difference is small enough that real-world application performance would likely feel nearly identical.

Looking at the broader benchmark landscape, the average benchmark score for the R5 M255 is 4788, derived from two tests (Geekbench OpenCL at 4650 and Geekbench Vulkan at 4925). The R8 M445DX has an average of 4727, based solely on its single OpenCL result. This means the R5 M255 actually holds a 1.3% higher average score than the R8 M445DX, despite losing the head-to-head OpenCL comparison. The Vulkan result for the R5 M255, which has no counterpart in the R8 M445DX's data set, is what lifts its average above the R8's score.

The nearest rival data confirms how close these two parts are. The R5 M255's rival list includes the R8 M445DX with a deltaPct of 1.3, meaning the R5 is 1.3% faster on average. Conversely, the R8 M445DX's rival list includes the R5 M255 with a deltaPct of -1.3, confirming the same relationship from the opposite direction. Both GPUs sit near the 27th-28th percentile of all GPUs, with the R5 M255 at 28 and the R8 M445DX at 27. These are entry-level mobile parts, positioned well below mainstream desktop GPUs.

The R5 M255 also shows interesting relationships with other rivals. It trails the NVIDIA GeForce RTX 3080 12 GB by a negligible 0.1% in average score, despite the massive architectural gulf between them. Against the NVIDIA GeForce 940MX, the R5 M255 is 1.2% slower. The AMD Radeon R5 M335 sits 0.8% below the R5 M255. For the R8 M445DX, it trails the R5 M335 by 0.5%, leads the NVIDIA Quadro P400 by 0.9%, and sits 1.3% behind both the R5 M255 and the RTX 3080 12 GB.

Architecture Differences

Both GPUs share the same fundamental architecture: GCN 3.0, built on a 28 nm process at TSMC. Both use a die measuring 125 mm² with 1,550 million transistors, yielding a transistor density of 12.4 million per mm². The chip names differ — Topaz for the R5 M255 and Meso for the R8 M445DX — but the underlying design family is identical.

The R5 M255 belongs to the "Gem System (R5 M200)" generation, while the R8 M445DX is part of the "Gem System Hybrid (Rx M400)" generation. This naming difference hints at a key architectural distinction: the R8 M445DX is designed as an integrated graphics processor (IGP) with a "System Shared" memory configuration, whereas the R5 M255 is a discrete-class part with dedicated memory.

Compute resources differ meaningfully. The R5 M255 has 384 shading units, 24 texture mapping units, and 8 raster operation pipelines. The R8 M445DX has fewer shading units at 320, fewer TMUs at 20, but retains 8 ROPs. This gives the R5 M255 a theoretical advantage in raw shader throughput and texture fill, though the R8's higher boost clock partially compensates.

Clock behavior is notably different. The R5 M255 runs at a base clock of 925 MHz and boosts to 940 MHz — a modest 15 MHz headroom. The R8 M445DX has a lower base clock of 780 MHz but a much higher boost clock of 1021 MHz, representing a 241 MHz boost range. This suggests the R8 M445DX can ramp up more aggressively under load, which helps explain its competitive benchmark showing despite fewer compute units.

Memory architecture is where the two diverge most sharply. The R5 M255 uses 2 GB of DDR3 memory on a 128-bit bus, delivering 32.00 GB/s of bandwidth. The R8 M445DX uses "System Shared" memory, meaning it relies on the host system's RAM with a bus width and bandwidth that are "System Dependent." This is a fundamental difference: dedicated memory versus shared memory. The R5's dedicated memory provides predictable bandwidth, while the R8's performance depends entirely on the laptop's system memory configuration.

Where Each One Wins

The benchmark data shows the R8 M445DX wins the only direct head-to-head test, the Geekbench OpenCL benchmark, by 1.6%. This is its sole confirmed victory. Given its higher boost clock of 1021 MHz versus 940 MHz, the R8 M445DX appears to benefit from aggressive clock scaling in OpenCL workloads that can utilize its boost headroom.

The R5 M255 wins in overall average benchmark score, 4788 versus 4727, a 1.3% advantage. This is driven entirely by its Geekbench Vulkan score of 4925, which is its best result. The R8 M445DX has no Vulkan benchmark data available, so the R5 M255 has a clear edge in Vulkan-capable applications. If a workload uses the Vulkan API, the data indicates the R5 M255 is the stronger choice.

The R5 M255 also wins on raw specifications. It has more shading units (384 versus 320), more TMUs (24 versus 20), and higher texture fill rate (22.56 GTexel/s versus 20.42 GTexel/s). Its FP32 throughput of 721.9 GFLOPS exceeds the R8's 653.4 GFLOPS. The R5 M255 also has dedicated memory with a fixed 32.00 GB/s bandwidth, which provides consistent performance regardless of system configuration. The R8 M445DX's shared memory setup means its actual bandwidth is unknown and variable.

The R8 M445DX wins on pixel rate. Its 8.168 GPixel/s exceeds the R5 M255's 7.520 GPixel/s, a consequence of its higher boost clock combined with the same 8 ROP count. This could give it a slight edge in fill-rate-bound scenarios, such as high-resolution rendering with simple shaders.

Specification Differences

The two GPUs differ across several specification fields. The R5 M255 uses the Topaz chip, while the R8 M445DX uses Meso. Their generations differ: "Gem System (R5 M200)" for the R5 M255 versus "Gem System Hybrid (Rx M400)" for the R8 M445DX.

Clock speeds differ substantially. The R5 M255 has a 925 MHz base clock and 940 MHz boost clock. The R8 M445DX has a 780 MHz base clock and 1021 MHz boost clock. Memory clocks also differ: the R5 M255 runs at 1000 MHz (2 Gbps effective), while the R8 M445DX uses "System Shared" memory with no fixed clock.

Memory configuration is the most significant difference. The R5 M255 has 2 GB of DDR3 on a 128-bit bus with 32.00 GB/s bandwidth. The R8 M445DX has "System Shared" memory size, type, bus width, and "System Dependent" bandwidth. The R5 M255 uses a PCIe 3.0 x8 bus interface, while the R8 M445DX is an IGP with no external bus interface.

Compute unit counts differ: 384 shading units and 24 TMUs for the R5 M255 versus 320 shading units and 20 TMUs for the R8 M445DX. Both have 8 ROPs. Pixel rates are 7.520 GPixel/s for the R5 M255 and 8.168 GPixel/s for the R8 M445DX. Texture rates are 22.56 GTexel/s and 20.42 GTexel/s respectively. FP32 throughput is 721.9 GFLOPS for the R5 M255 and 653.4 GFLOPS for the R8 M445DX. Both have 1:1 FP16 ratios.

The R8 M445DX lists "Portable Device Dependent" display outputs and slot width as "IGP," while the R5 M255 has no display output or slot width data. Release dates differ: the R5 M255 launched on October 11, 2014, while the R8 M445DX launched on May 14, 2016. Both are end-of-life products. The R5 M255 lists its predecessor as "Solar System" and successor as "Polaris Mobile," while the R8 M445DX has neither. Neither has a launch MSRP. Both support DirectX 12 (12_0), OpenGL 4.6, and Vulkan 1.2.170.

FAQ

Q: Which GPU has a higher average benchmark score?

A: The AMD Radeon R5 M255 has an average benchmark score of 4788, compared to 4727 for the AMD Radeon R8 M445DX, a difference of 1.3%.

Q: Does the R8 M445DX ever beat the R5 M255?

A: Yes, in the Geekbench OpenCL test, the R8 M445DX scores 4727 versus 4650 for the R5 M255, a 1.6% advantage.

Q: What is the memory configuration difference?

A: The R5 M255 has 2 GB of dedicated DDR3 memory on a 128-bit bus with 32.00 GB/s bandwidth. The R8 M445DX uses System Shared memory with System Dependent bandwidth, meaning it relies on the host system's RAM.

Q: Which GPU has more shading units?

A: The R5 M255 has 384 shading units, while the R8 M445DX has 320 shading units. The R5 M255 also has 24 TMUs versus 20 TMUs for the R8 M445DX.

Q: How do their boost clocks compare?

A: The R8 M445DX has a higher boost clock of 1021 MHz, compared to 940 MHz for the R5 M255. However, the R5 M255 has a higher base clock of 925 MHz versus 780 MHz for the R8 M445DX.

Q: Do they support the same APIs?

A: Yes, both support DirectX 12 (12_0), OpenGL 4.6, and Vulkan 1.2.170. However, the R5 M255 has a Vulkan benchmark score of 4925, while the R8 M445DX has no Vulkan benchmark data.

The Verdict

The benchmark data shows two closely matched entry-level mobile GPUs with different design philosophies. The R8 M445DX wins the single direct head-to-head OpenCL test by 1.6%, but the R5 M255 holds a 1.3% higher average benchmark score thanks to its Vulkan performance. Users who prioritize OpenCL performance in the specific test scenario should lean toward the R8 M445DX. Users who may run Vulkan-based applications should choose the R5 M255, as it has a demonstrated Vulkan score of 4925 while the R8 M445DX has no Vulkan data at all.

The R5 M255 offers more compute resources — 384 shading units versus 320, 24 TMUs versus 20 — and higher theoretical throughput in FP32 (721.9 GFLOPS versus 653.4 GFLOPS) and texture fill (22.56 GTexel/s versus 20.42 GTexel/s). Its dedicated 2 GB DDR3 memory with 32.00 GB/s bandwidth provides consistent, predictable performance. The R8 M445DX counters with a higher boost clock (1021 MHz versus 940 MHz) and a higher pixel rate (8.168 GPixel/s versus 7.520 GPixel/s), but its shared memory architecture makes real-world performance dependent on the host system.

The percentile rankings are nearly identical — 28th for the R5 M255, 27th for the R8 M445DX — confirming these are equivalent-tier products. The R5 M255 is the safer choice for consistent performance and Vulkan support, while the R8 M445DX offers a small OpenCL edge and benefits from being a later release. Given the R5 M255's higher average score and its additional Vulkan capability, the data marginally favors the R5 M255 for general use, though the R8 M445DX's OpenCL win keeps the decision close.