AMD Radeon R5 M255 vs AMD Radeon R5 M420 Comparison

The Verdict

The recorded data places the AMD Radeon R5 M255 ahead of the AMD Radeon R5 M420 in the single shared benchmark, Geekbench OpenCL. The M255 scores 4650, while the M420 scores 3956, a delta of -14.9% for the older part. The M255 also holds a higher overall percentile rank at 28 versus the M420's 23, meaning it outperforms a larger share of all GPUs in the database.

For users seeking the stronger compute performance in an end-of-life mobile GPU, the M255 is the clear pick. Its average benchmark score of 4788 (based on both OpenCL and Vulkan results) sits well above the M420's single OpenCL score of 3956. The M255's nearest rivals include the NVIDIA GeForce 940MX at 4844 (1.2% higher) and the AMD Radeon R5 M335 at 4752 (0.8% lower), placing it in a competitive bracket for lightweight laptops. The M420, by contrast, lands near the NVIDIA GeForce 830M (3957, 0% delta) and the NVIDIA GeForce GT 745M (3953, 0.1% higher), showing it is a step below in raw compute.

However, the M420 does have one practical advantage: memory capacity. It ships with 4 GB DDR3, while the M255 offers 2 GB DDR3. For workloads that require larger frame buffers or allocate more memory for compute tasks, the M420 may be the safer choice despite its lower throughput. The M255 counters with double the memory bus width (128 bit versus 64 bit) and double the bandwidth (32.00 GB/s versus 16.00 GB/s), which heavily favors it in memory-bound scenarios. The choice ultimately depends on whether the user prioritizes compute speed or memory capacity, but benchmark results indicate the M255 is the faster part in most measurable ways.

Architecture Differences

The two GPUs come from different architectural generations within AMD's GCN family. The M420 uses GCN 1.0 with a chip codename "Jet", while the M255 uses GCN 3.0 with a chip codename "Topaz". Both are built on a 28 nm process at TSMC, but the transistor counts differ substantially. The M420 packs 690 million transistors on a 56 mm² die, while the M255 contains 1,550 million transistors on a 125 mm² die. Transistor density is nearly identical (12.3M per mm² for the M420, 12.4M per mm² for the M255), indicating the process node is the same, but the M255's larger die allows for more execution resources.

The M255's GCN 3.0 architecture brings a higher compute configuration. It has 384 shading units, 24 texture mapping units (TMUs), and 8 render output units (ROPs). The M420, on GCN 1.0, has 320 shading units, 20 TMUs, and the same 8 ROPs. The M255 also supports FP16 at a 1:1 ratio with FP32, offering 721.9 GFLOPS for both precisions. The M420 has no recorded FP16 capability, so it relies on FP32 only at 544.0 GFLOPS.

Clock speeds favor the M255 as well. Its base clock is 925 MHz with a boost to 940 MHz, compared to the M420's 780 MHz base and 850 MHz boost. Memory clocks are identical at 1000 MHz with 2 Gbps effective, but the memory subsystem differs. The M420 uses a 64-bit bus with 16.00 GB/s bandwidth and 4 GB DDR3. The M255 uses a 128-bit bus with 32.00 GB/s bandwidth and 2 GB DDR3.

API support also differs. The M420 supports DirectX 12 (11_1), while the M255 supports DirectX 12 (12_0). Both support OpenGL 4.6 and Vulkan 1.2.170, so API-level compatibility is otherwise similar. The M255's higher DirectX feature level may matter for certain modern titles, though the performance gap in the benchmark data is modest.

FAQ

Q: Which GPU has the higher benchmark score?

A: The AMD Radeon R5 M255 scores 4650 in Geekbench OpenCL, while the AMD Radeon R5 M420 scores 3956. The M255 also has a Vulkan score of 4925, giving it an average benchmark score of 4788 compared to the M420's 3956.

Q: How does the memory configuration differ?

A: The M420 has 4 GB DDR3 on a 64-bit bus with 16.00 GB/s bandwidth. The M255 has 2 GB DDR3 on a 128-bit bus with 32.00 GB/s bandwidth. The M255 provides double the bandwidth, while the M420 provides double the capacity.

Q: Are both GPUs based on the same architecture?

A: No. The M420 uses GCN 1.0, while the M255 uses GCN 3.0. Both are built on a 28 nm TSMC process, but the M255 has a larger die and more transistors.

Q: What is the DirectX support difference?

A: The M420 supports DirectX 12 (11_1), while the M255 supports DirectX 12 (12_0). Both support OpenGL 4.6 and Vulkan 1.2.170.

Q: Which GPU is better relative to its closest competitors?

A: The M255 sits at the 28th percentile among all GPUs, with its nearest rival being the NVIDIA GeForce 940MX at 4844 (1.2% higher). The M420 sits at the 23rd percentile, with its nearest rival being the NVIDIA GeForce 830M at 3957 (0% delta). The M255 competes in a higher performance tier.

Q: Is the M255 faster in every benchmark?

A: The database contains only one head-to-head benchmark result: Geekbench OpenCL. The M255 wins that test with 4650 versus 3956, a delta of -14.9%. No other direct comparisons are recorded, so the M255's advantage in this single test is the only measurable win.

Specification Differences

The following fields differ between the AMD Radeon R5 M420 and the AMD Radeon R5 M255:

• Chip: Jet versus Topaz
• Architecture: GCN 1.0 versus GCN 3.0
• Generation: Gem System (R5 M400) versus Gem System (R5 M200)
• Transistors: 690 million versus 1,550 million
• Die Size: 56 mm² versus 125 mm²
• Transistor Density: 12.3M / mm² versus 12.4M / mm²
• Base Clock: 780 MHz versus 925 MHz
• Boost Clock: 850 MHz versus 940 MHz
• Memory Size: 4 GB versus 2 GB
• Memory Bus Width: 64 bit versus 128 bit
• Memory Bandwidth: 16.00 GB/s versus 32.00 GB/s
• Shading Units: 320 versus 384
• TMUs: 20 versus 24
• Pixel Rate: 6.800 GPixel/s versus 7.520 GPixel/s
• Texture Rate: 17.00 GTexel/s versus 22.56 GTexel/s
• FP32: 544.0 GFLOPS versus 721.9 GFLOPS
• FP16: Not recorded versus 721.9 GFLOPS (1:1)
• DirectX: 12 (11_1) versus 12 (12_0)
• Slot Width: IGP versus not recorded
• Display Outputs: Portable Device Dependent versus not recorded
• Release Date: 2016-05-14 versus 2014-10-11

Fields that are identical include the manufacturer (AMD), process node (28 nm), foundry (TSMC), memory type (DDR3), memory clock (1000 MHz, 2 Gbps effective), ROPs (8), bus interface (PCIe 3.0 x8), OpenGL (4.6), Vulkan (1.2.170), production status (End-of-life), predecessor (Solar System), and successor (Polaris Mobile). Neither GPU has a recorded TDP, power connector, suggested PSU, or launch MSRP.

Head-to-Head Benchmarks

The database records one head-to-head benchmark between these two GPUs: Geekbench OpenCL. The M255 wins decisively with a score of 4650, while the M420 trails at 3956. The delta percentage is -14.9%, meaning the M420 is 14.9% slower than the M255 in this test.

This OpenCL result aligns with the raw specification differences. The M255 has 384 shading units versus 320, a 20% increase in compute units. Its FP32 throughput of 721.9 GFLOPS is about 32.7% higher than the M420's 544.0 GFLOPS, and its texture rate of 22.56 GTexel/s is about 32.7% higher than the M420's 17.00 GTexel/s. The M255 also benefits from a higher boost clock (940 MHz versus 850 MHz) and more than double the memory bandwidth (32.00 GB/s versus 16.00 GB/s).

The M255 also has a recorded Geekbench Vulkan score of 4925, which is not available for the M420. This Vulkan result contributes to the M255's average benchmark score of 4788, further separating it from the M420's single OpenCL score of 3956. The M255's nearest rival in the database is the NVIDIA GeForce RTX 3080 12 GB, which scores 4791 and is 0.1% higher. This is a notable comparison: the M255, a low-end mobile GPU from 2014, benchmarks within a rounding error of a high-end desktop part from a much later generation in this specific OpenCL workload. That result should be read with caution, as the database's percentile ranking (28 for the M255) places it firmly in the lower half of all GPUs.

The M420's nearest rival is the NVIDIA GeForce 830M at 3957, a 0% delta, meaning the two are statistically tied. The M420 also sits within 0.5% of the AMD Radeon HD 6850 X2 (3977) and within 0.2% of the NVIDIA Quadro K2000 (3964). These are all older or lower-tier parts, confirming the M420's position at the lower end of the performance spectrum.

In summary, the head-to-head data shows a single clear win for the M255. The M420 does not win any recorded benchmark, and its only advantage is memory capacity (4 GB versus 2 GB). For compute-heavy tasks, the M255 is the superior choice by a 14.9% margin in OpenCL, and its Vulkan support adds another data point in its favor. The M420 remains a viable option for users who need more video memory, but the performance gap is significant enough that the M255 is the better pick for most workloads.