AMD Radeon R5 M255 vs AMD Radeon R7 M340 Comparison

The AMD Radeon R7 M340 and AMD Radeon R5 M255 are both end-of-life mobile graphics solutions built on the same GCN 3.0 architecture and 28 nm TSMC process, yet they occupy slightly different performance tiers. Benchmark data from Geekbench shows the R7 M340 winning both head-to-head tests, with a 6.1% lead in OpenCL and a 5.4% lead in Vulkan, translating to an average benchmark score of 5063 versus 4788 for the R5 M255. The R7 M340 sits at the 30th percentile of all GPUs, while the R5 M255 is at the 28th, meaning neither is a powerhouse by modern standards, but the R7 M340 is consistently the faster part in compute workloads.

The Verdict

The data points to a clear, if modest, winner: the AMD Radeon R7 M340. It outperforms the R5 M255 in every recorded benchmark, achieving 4932 in Geekbench OpenCL and 5193 in Vulkan, versus 4650 and 4925 respectively for the R5 M255. The R7 M340’s average score of 5063 ties it exactly with the AMD Radeon R7 240, while the R5 M255’s 4788 average puts it in the company of the NVIDIA GeForce 940MX, which scores 4844.

Users choosing between these two should pick the R7 M340 if raw compute performance is the priority, as it is 5-6% faster across the board. The R5 M255, however, offers a wider memory bus (128-bit versus 64-bit) and double the memory bandwidth, which could matter in certain memory-sensitive workloads despite its lower compute scores. Neither GPU will satisfy modern gaming demands, as their 28th and 30th percentiles indicate they are among the slower GPUs in the database. For legacy systems or basic acceleration tasks, the R7 M340 is the safer choice based purely on the benchmark results.

Architecture Differences

Both GPUs share the same fundamental architecture: GCN 3.0, fabricated on a 28 nm process at TSMC, with 1,550 million transistors on a 125 mm² die, yielding a transistor density of 12.4M per mm². They also share identical API support, including DirectX 12 (12_0), OpenGL 4.6, and Vulkan 1.2.170, as well as the same PCIe 3.0 x8 bus interface. The production status for both is end-of-life, and both list Solar System as their predecessor and Polaris Mobile as their successor.

The key differences lie in the chip configuration and clocks. The R7 M340 uses the Meso chip with a base clock of 943 MHz and a boost clock of 1021 MHz, while the R5 M255 uses the Topaz chip with a lower base of 925 MHz and a boost of 940 MHz. Despite the R7 M340’s higher clocks, the R5 M255 packs more execution resources: 384 shading units, 24 texture mapping units (TMUs), and 8 raster operation units (ROPs), compared to the R7 M340’s 320 shading units, 20 TMUs, and 8 ROPs. This gives the R5 M255 a theoretical FP32 throughput of 721.9 GFLOPS and a texture rate of 22.56 GTexel/s, versus 653.4 GFLOPS and 20.42 GTexel/s for the R7 M340.

Memory configuration is where the R5 M255 counters its compute deficit. Both use 2 GB of DDR3 at 1000 MHz (2 Gbps effective), but the R5 M255 has a 128-bit bus width, delivering 32.00 GB/s of bandwidth. The R7 M340 is limited to a 64-bit bus, halving bandwidth to 16.00 GB/s. The R7 M340 does achieve a higher pixel rate of 8.168 GPixel/s versus 7.520 GPixel/s for the R5 M255, but the R5 M255’s superior raw shader count and bandwidth suggest it may handle certain workloads with more headroom, even if the benchmark scores say otherwise.

Head-to-Head Benchmarks

The benchmark data is unambiguous: the R7 M340 wins both recorded tests. In Geekbench OpenCL, the R7 M340 scores 4932 against 4650 for the R5 M255, a delta of 6.1%. In Geekbench Vulkan, the margin narrows slightly to 5.4%, with scores of 5193 and 4925 respectively. This translates to a total of 2 wins for the R7 M340 and 0 for the R5 M255 in the head-to-head comparison.

The R7 M340’s average benchmark score of 5063 places it exactly level with the AMD Radeon R7 240, and just 0.6% ahead of the AMD FirePro W4170M (5034) and 0.9% ahead of the Radeon R5 M430 (5018). The R5 M255’s average of 4788, meanwhile, is nearly identical to the NVIDIA GeForce RTX 3080 12 GB (4791), a delta of -0.1%, though that comparison is likely an artifact of the benchmark database rather than a realistic performance equivalence. More relevantly, the R5 M255 is 0.8% ahead of the Radeon R5 M335 (4752) and 1.3% ahead of the Radeon R8 M445DX (4727), but 1.2% behind the GeForce 940MX (4844).

The biggest win for the R7 M340 is in OpenCL, where its 6.1% advantage is the largest recorded gap between the two. The Vulkan test shows a tighter race, but the R7 M340 still comes out ahead. The data suggests that the R7 M340’s higher clock speeds (943/1021 MHz versus 925/940 MHz) are enough to overcome the R5 M255’s extra 64 shading units in these specific compute workloads. The R5 M255’s doubled memory bandwidth does not translate into a win in either benchmark, indicating that these tests are compute-bound rather than bandwidth-bound.

FAQ

Q: Which GPU has a higher average benchmark score?

A: The AMD Radeon R7 M340 has a higher average benchmark score of 5063, compared to 4788 for the AMD Radeon R5 M255.

Q: How much faster is the R7 M340 in Geekbench OpenCL?

A: The R7 M340 scores 4932 versus 4650 for the R5 M255, making it 6.1% faster in that test.

Q: Does the R5 M255 have any advantages in memory configuration?

A: Yes, the R5 M255 has a 128-bit memory bus and 32.00 GB/s bandwidth, while the R7 M340 has a 64-bit bus and 16.00 GB/s bandwidth. Both use 2 GB of DDR3 memory.

Q: Are these GPUs still in production?

A: No, both are marked as end-of-life in the database. The R7 M340 was released in May 2015, and the R5 M255 was released in October 2014.

Q: What are the shading unit counts for each GPU?

A: The R5 M255 has 384 shading units, while the R7 M340 has 320 shading units.

Q: How do these GPUs compare to the AMD Radeon R7 240?

A: The R7 M340 has an identical average score of 5063 to the R7 240, while the R5 M255 is lower at 4788.

Where Each One Wins

The AMD Radeon R7 M340 wins in every measured benchmark category. It takes the Geekbench OpenCL test with a 6.1% margin and the Geekbench Vulkan test with a 5.4% margin, making it the clear choice for compute-heavy tasks like OpenCL acceleration or Vulkan-based rendering. Its higher clock speeds (1021 MHz boost versus 940 MHz) and superior pixel rate (8.168 GPixel/s versus 7.520 GPixel/s) give it an edge in fill-rate-bound scenarios. The R7 M340 also matches the performance of the Radeon R7 240 exactly, making it a familiar baseline for users upgrading from that desktop part.

The AMD Radeon R5 M255, despite losing all head-to-head benchmarks, has specific hardware advantages that could favor certain use cases. Its 128-bit memory bus and 32.00 GB/s bandwidth are double that of the R7 M340, which could be beneficial in memory-intensive applications like large texture loads or higher-resolution framebuffers. The R5 M255 also has more shading units (384 versus 320), more TMUs (24 versus 20), and higher theoretical FP32 throughput (721.9 GFLOPS versus 653.4 GFLOPS), suggesting it has more raw compute headroom that the current benchmarks do not fully capture. Its texture rate of 22.56 GTexel/s also exceeds the R7 M340’s 20.42 GTexel/s, which might translate to better performance in games that rely heavily on texturing rather than compute.

In practical terms, the R7 M340 is the winner for anyone relying on the specific benchmarks in this database. The R5 M255’s advantages are theoretical and did not manifest in the recorded tests. However, for users who know their workloads are bandwidth-limited or shader-heavy, the R5 M255’s architecture could be the better fit, even if the aggregate data points to the R7 M340 as the faster part. Both GPUs are old, end-of-life products, and the data shows they are closely matched, with the R7 M340 holding a consistent single-digit percentage lead across all tests.