AMD Radeon R5 M255 vs NVIDIA GeForce GT 645M Comparison

Head-to-Head Benchmarks

The two benchmark results provided in the data show a clear, though not entirely uniform, advantage for the AMD Radeon R5 M255. In the Geekbench OpenCL test, the AMD part posts a score of 4650 against the NVIDIA GeForce GT 645M's 2680. This represents a commanding 73.5% lead for the AMD GPU, indicating a substantial gap in compute throughput under the OpenCL API. The margin here is decisive; the AMD R5 M255 is in a different performance tier for this workload.

The second test, Geekbench Vulkan, tells a much closer story. The AMD Radeon R5 M255 scores 4925, while the NVIDIA GeForce GT 645M trails with 4875. The delta between them shrinks to a razor-thin 1% in favor of the AMD part. This near-tie in the Vulkan test suggests that when both GPUs are utilized through a modern, low-level graphics API, the architectural differences largely cancel out in terms of raw benchmark output. The NVIDIA GPU, despite its much larger deficit in OpenCL, manages to claw back nearly all of the ground in this particular test.

Looking at the broader benchmark context, the R5 M255's average benchmark score is 4788, with a percentile rank of 28 among all GPUs. The GT 645M's average is 4411, placing it at the 26th percentile. The 377-point gap in average scores aligns with the head-to-head results, showing that the AMD part holds a consistent, if sometimes small, edge across the aggregate of its benchmark runs. The AMD GPU's nearest rival, the NVIDIA GeForce RTX 3080 12 GB, scores an average of 4791, a delta of only -0.1%, which contextualizes the R5 M255's performance as being surprisingly close to a much higher-tier product in this synthetic metric. For the NVIDIA GT 645M, its nearest rival is the AMD Radeon R7 M260, which scores 4499, putting the GT 645M -1.9% behind its closest competitor.

The Verdict

The data unequivocally points to the AMD Radeon R5 M255 as the faster GPU. It wins both head-to-head benchmark tests, securing 2 wins to the NVIDIA GeForce GT 645M's 0. The most important single data point is the 73.5% advantage in Geekbench OpenCL, which is a massive lead that no amount of architectural nuance can overcome. While the Vulkan test shows a near-parity, a win is still a win, and the AMD part takes it.

From a pure performance standpoint, there is no argument for the GT 645M based on the benchmark results. The data shows that the R5 M255 is the superior product. The GT 645M's only consolation is its 32 W TDP, which suggests it may be a more power-efficient part, but the benchmark data does not include any power efficiency metrics to confirm this. The R5 M255 has no listed TDP, so a direct power comparison is impossible from the facts provided. The R5 M255 also holds a higher percentile rank (28th vs 26th), further solidifying its position as the better-performing part. Users looking for the highest benchmark scores should choose the AMD Radeon R5 M255 without hesitation.

Where Each One Wins

The AMD Radeon R5 M255 wins in the compute-heavy OpenCL workload by a landslide. Its 4650 score versus 2680 for the NVIDIA part shows a clear dominance in general-purpose GPU compute tasks that leverage OpenCL. This makes the AMD part the better choice for any application that relies heavily on this API for acceleration. The R5 M255 also wins, albeit narrowly, in the Vulkan graphics test, making it the better choice for gaming or graphics workloads that utilize Vulkan, even if the margin is slight.

The NVIDIA GeForce GT 645M does not win any benchmark tests. However, it possesses a distinct advantage in power consumption, with a specified TDP of 32 W. The R5 M255's TDP is not listed in the data, but the GT 645M's official rating suggests it might be a more suitable option for thermally constrained environments, such as thin laptops where sustained performance is less critical than keeping temperatures and power draw low. The GT 645M also has a wider bus interface (PCIe 3.0 x16 vs x8), which could theoretically offer better bandwidth for data transfer, but this does not translate into a benchmark win. Its higher pixel rate (6.240 GPixel/s) and texture rate (24.96 GTexel/s) compared to the R5 M255's 7.520 GPixel/s and 22.56 GTexel/s respectively, show a mixed bag; the GT 645M has a higher texture fill rate but lower pixel fill rate, yet this does not yield a victory in the provided tests.

FAQ

Q: Which GPU has the higher average benchmark score?

A: The AMD Radeon R5 M255 has a higher average benchmark score of 4788, compared to the NVIDIA GeForce GT 645M's average of 4411.

Q: How much faster is the AMD Radeon R5 M255 in Geekbench OpenCL?

A: The AMD Radeon R5 M255 scores 4650 in Geekbench OpenCL, which is 73.5% higher than the NVIDIA GeForce GT 645M's score of 2680.

Q: Is there any benchmark where the NVIDIA GeForce GT 645M wins?

A: No. In the head-to-head benchmarks, the AMD Radeon R5 M255 wins both the Geekbench OpenCL and Geekbench Vulkan tests. The NVIDIA GPU has zero wins.

Q: What is the difference in Vulkan performance between the two cards?

A: The difference is minimal. The AMD Radeon R5 M255 scores 4925, while the NVIDIA GeForce GT 645M scores 4875, resulting in only a 1% delta in favor of the AMD part.

Q: What are the transistor counts for each GPU?

A: The AMD Radeon R5 M255 has 1,550 million transistors, while the NVIDIA GeForce GT 645M has 1,270 million transistors.

Q: What is the TDP of the NVIDIA GeForce GT 645M?

A: The NVIDIA GeForce GT 645M has a TDP of 32 W. The TDP for the AMD Radeon R5 M255 is not listed in the data.

Architecture Differences

The two GPUs are built on fundamentally different architectures from their respective manufacturers. The AMD Radeon R5 M255 is based on the GCN 3.0 architecture, using the "Topaz" chip, while the NVIDIA GeForce GT 645M uses the Kepler architecture with the GK107 chip. Both are manufactured on a 28 nm process node at TSMC, but the AMD chip has a higher transistor count of 1,550 million versus 1,270 million for the NVIDIA part. The die size is also slightly larger on the AMD side at 125 mm² compared to 118 mm², giving it a higher transistor density of 12.4M / mm² versus 10.8M / mm².

In terms of core configuration, both GPUs feature 384 shading units. However, the NVIDIA GeForce GT 645M has a higher number of texture mapping units (TMUs) at 32, compared to 24 on the AMD Radeon R5 M255, and double the render output units (ROPs) at 16 versus 8. This configuration explains the GT 645M's higher texture rate of 24.96 GTexel/s, while the R5 M255 compensates with a higher pixel rate of 7.520 GPixel/s. The AMD part also has a higher FP32 performance rating of 721.9 GFLOPS, which is consistent with its dominant OpenCL score. Interestingly, the AMD R5 M255 has an FP16 performance of 721.9 GFLOPS (1:1), while the NVIDIA GT 645M has no FP16 data listed.

Memory subsystems are similar in capacity and type: both have 2 GB of DDR3 memory on a 128-bit bus. However, the AMD Radeon R5 M255's memory runs at 1000 MHz (2 Gbps effective), delivering a bandwidth of 32.00 GB/s, while the NVIDIA GeForce GT 645M's memory runs at 900 MHz (1800 Mbps effective), resulting in a lower bandwidth of 28.80 GB/s. The bus interfaces also differ, with the AMD part using PCIe 3.0 x8 and the NVIDIA part using PCIe 3.0 x16. In terms of API support, the AMD R5 M255 supports DirectX 12 (12_0), OpenGL 4.6, and Vulkan 1.2.170. The NVIDIA GT 645M also supports DirectX 12, but at the lower feature level of 11_0, while matching OpenGL 4.6 and slightly exceeding Vulkan support at 1.2.175. The NVIDIA part is listed as an IGP (integrated graphics processor) with no power connectors, while the AMD part has no slot width or power connector data listed.