NVIDIA GeForce 825M vs NVIDIA GeForce GT 645M Comparison

Head-to-Head Benchmarks

The database contains a single directly comparable benchmark result for these two mobile graphics processors: Geekbench OpenCL. In that test, the NVIDIA GeForce 825M posts a score of 3694, while the NVIDIA GeForce GT 645M records 2680. This gives the 825M a decisive victory with a delta of 27.4% over its older counterpart. The margin is substantial for a single test, indicating that the newer chip holds a clear performance advantage in general compute workloads that leverage OpenCL.

Beyond the head-to-head, the average benchmark scores in the database reinforce this separation. The GT 645M carries an average score of 4411, but this figure is buoyed by its additional results in Geekbench Metal (5679) and Geekbench Vulkan (4875). The 825M, by contrast, only has the OpenCL result recorded, so its average score of 3694 is identical to its single test result. When comparing averages, the GT 645M appears higher, but this is misleading because the two chips do not share the same test suite in the database. The only true apples-to-apples comparison is the OpenCL run, where the 825M wins outright.

The percentile rankings also tell a consistent story. The GT 645M sits at the 26th percentile of all GPUs in the database, while the 825M rests at the 22nd percentile. Despite the 825M's higher raw OpenCL score, its overall standing is slightly lower because it lacks the additional benchmark data points that push the GT 645M's average upward. This discrepancy highlights the importance of interpreting scores within the context of which tests were actually executed.

For the GT 645M, its nearest rivals in the database include the NVIDIA GeForce 930M (average score 4388, delta 0.5%), the Intel Iris Pro Graphics 5200 (4360, delta 1.2%), and the NVIDIA GeForce RTX 4070 GDDR6 (4335, delta 1.8%). These deltas are all within 2%, meaning the GT 645M's average performance is tightly clustered with these very different GPUs. On the losing side, the AMD Radeon R7 M260 sits 1.9% ahead of the GT 645M, which is notable because that AMD chip outperforms the NVIDIA part in the database's aggregate metric.

The 825M's nearest rivals show a similar pattern of closeness. The NVIDIA GeForce GT 740M (average 3717) is 0.6% behind, the NVIDIA Quadro 3000M (3718) is 0.6% behind, and the NVIDIA GeForce GT 635M (3740) is 1.2% behind. Meanwhile, the AMD Radeon HD 6770 (3649) trails the 825M by 1.2%. These narrow margins place the 825M in a competitive band of older mobile and desktop parts, none of which hold a commanding lead.

FAQ

Q: Which GPU wins the only direct benchmark comparison in the database?

A: The NVIDIA GeForce 825M wins the Geekbench OpenCL test with a score of 3694, beating the NVIDIA GeForce GT 645M's score of 2680 by 27.4%.

Q: Does the GT 645M have any benchmark wins over the 825M?

A: No. The head-to-head data records zero wins for the GT 645M and one win for the 825M. The GT 645M does have additional scores in Metal and Vulkan, but the 825M has no results in those tests, so no comparison is possible.

Q: How do the two GPUs compare in overall database percentile rankings?

A: The GT 645M ranks at the 26th percentile of all GPUs, while the 825M ranks at the 22nd percentile. This puts the GT 645M slightly higher in the overall distribution, despite losing the direct OpenCL comparison.

Q: What is the average benchmark score for each GPU?

A: The GT 645M has an average benchmark score of 4411, while the 825M has an average of 3694. The GT 645M's average is pulled up by its Metal and Vulkan scores, which the 825M does not have.

Q: Are these two GPUs closely matched to similar rivals in the database?

A: Yes. The GT 645M's nearest rivals are all within 1.8% of its average score, including the GeForce 930M, Iris Pro 5200, and RTX 4070 GDDR6. The 825M's nearest rivals are within 1.2%, including the GT 740M and Quadro 3000M.

Q: Which GPU has a higher raw floating-point performance in the database?

A: The 825M is rated at 722.7 GFLOPS FP32, while the GT 645M is rated at 599.0 GFLOPS FP32. This aligns with the 825M's higher OpenCL score.

Where Each One Wins

The 825M wins the only directly comparable benchmark, the Geekbench OpenCL test, with a 27.4% margin. This is the clearest victory in the data. The 825M also holds higher raw throughput rates: its pixel rate is 7.528 GPixel/s versus 6.240 GPixel/s for the GT 645M, and its texture rate is 30.11 GTexel/s versus 24.96 GTexel/s. These figures indicate that the 825M is faster at filling pixels and processing textures, which are core operations in rendering. Its FP32 compute rating of 722.7 GFLOPS also exceeds the GT 645M's 599.0 GFLOPS by roughly 20.6%.

The GT 645M, however, wins in the broader database standings. Its average benchmark score of 4411 is higher than the 825M's 3694, and its percentile rank of 26 is above the 825M's 22. This is driven by its performance in Geekbench Metal (5679) and Geekbench Vulkan (4875), two modern API tests where the 825M has no recorded data. For users prioritizing those specific workloads, the GT 645M demonstrates capability that the 825M cannot claim in the database.

The GT 645M also wins on memory bandwidth. It offers 28.80 GB/s of bandwidth versus 14.40 GB/s for the 825M, and its 128-bit memory bus is twice as wide as the 825M's 64-bit bus. This suggests that the GT 645M may handle memory-intensive workloads more effectively, even if its raw compute is lower. The GT 645M also has double the memory capacity at 2 GB versus 1024 MB.

Specification Differences

The two GPUs differ in several key specifications. The GT 645M uses the GK107 chip, while the 825M uses the GK208 chip. The GT 645M has a transistor count of 1,270 million on a die size of 118 mm², giving a transistor density of 10.8M per mm². The 825M has 1,020 million transistors on a smaller 87 mm² die, yielding a higher density of 11.7M per mm². The 825M is therefore a more compact design with fewer transistors but tighter packing.

Clock speeds differ significantly. The GT 645M runs at 709 MHz base and 780 MHz boost, while the 825M runs at 850 MHz base and 941 MHz boost. This gives the 825M a 141 MHz advantage at base and a 161 MHz advantage at boost. Both GPUs use DDR3 memory at 900 MHz with 1800 Mbps effective, so memory clock is identical. However, the GT 645M has a 128-bit memory bus versus 64-bit for the 825M, resulting in doubled bandwidth (28.80 GB/s vs 14.40 GB/s) and double the memory capacity (2 GB vs 1024 MB).

The shading unit count is identical: both have 384 shading units and 32 texture mapping units. The ROP count differs, with the GT 645M having 16 ROPs and the 825M having 8. This explains why the 825M achieves a higher pixel rate (7.528 GPixel/s) despite fewer ROPs: its much higher clock speed compensates. The bus interface also differs: the GT 645M uses PCIe 3.0 x16, while the 825M uses PCIe 3.0 x8.

Power consumption is nearly the same, with the GT 645M rated at 32 W and the 825M at 33 W. Both are listed as integrated graphics packages (IGP) with no power connectors and portable-device-dependent display outputs. The GT 645M was released earlier, on 2012-09-30, while the 825M came later on 2014-01-26. The GT 645M belongs to the GeForce 600M generation and the 825M to the GeForce 800M generation.

Architecture Differences

The GT 645M is built on the Kepler architecture, while the 825M is built on Kepler 2.0. Both use a 28 nm process at TSMC, but the architectural revision matters. Kepler 2.0 introduces refinements that allow higher clock speeds at similar power draw. This is evident in the 825M's 850 MHz base clock compared to the GT 645M's 709 MHz base, despite both having the same 384 shading units.

The chip designs diverge in die size and transistor budget. The GK107 in the GT 645M is larger at 118 mm² with 1,270 million transistors. The GK208 in the 825M is smaller at 87 mm² with 1,020 million transistors. The 825M achieves a higher transistor density (11.7M / mm²) than the GT 645M (10.8M / mm²), indicating a more efficient layout. This density advantage, combined with the higher clocks, is why the 825M delivers superior compute performance (722.7 GFLOPS vs 599.0 GFLOPS) while consuming nearly identical power (33 W vs 32 W).

The memory architecture differs substantially. The GT 645M pairs its larger die with a 128-bit memory interface, enabling 28.80 GB/s of bandwidth. The 825M halves the bus to 64-bit, capping bandwidth at 14.40 GB/s. This is a deliberate trade-off: the 825M prioritizes compute throughput and clock speed, while the GT 645M allocates more silicon to memory throughput. The ROP count also halves from 16 to 8, yet the 825M still produces a higher pixel rate due to its clock advantage.

Both GPUs support identical API feature sets: DirectX 12 (11_0), OpenGL 4.6, and Vulkan 1.2.175. Neither has ray tracing cores or tensor cores. The 825M's Kepler 2.0 update does not introduce new API capabilities in the database records; the differences are purely in clock speeds, memory layout, and physical design. The GT 645M's predecessor is the GeForce 500M series and its successor is the GeForce 700M series. The 825M's predecessor is the GeForce 700M series and its successor is the GeForce 900M series.

The Verdict

The data presents a clear split decision. For raw compute performance in OpenCL, the NVIDIA GeForce 825M is the superior part. Its 27.4% lead in the head-to-head test is backed by higher clock speeds (850 MHz base vs 709 MHz), higher FP32 throughput (722.7 GFLOPS vs 599.0 GFLOPS), and faster pixel/texture rates. If the workload is heavily compute-bound and uses OpenCL, the 825M is the obvious choice.

However, the GT 645M offers advantages that may matter in specific scenarios. Its 28.80 GB/s of memory bandwidth is double the 825M's 14.40 GB/s, and its 2 GB frame buffer is twice as large. For applications that are memory-bound or require larger textures and assets, the GT 645M could hold an edge despite its lower compute. The GT 645M also shows stronger results in Metal and Vulkan tests, though the 825M has no recorded scores in those tests, so this is not a direct comparison.

The average benchmark score favors the GT 645M (4411 vs 3694), and its percentile rank is higher (26 vs 22). Buyers or system builders who rely on the database's aggregate metric would see the GT 645M as the better-rounded part. Yet the single direct comparison shows the 825M winning by a wide margin. The recorded data does not include a Metal or Vulkan result for the 825M, so any judgment about those APIs is incomplete.

In practical terms, the 825M is the better choice for users who prioritize modern compute workloads and can accept a narrower memory bus. The GT 645M is better for users who need memory capacity and bandwidth, particularly for texture-heavy content or higher resolution assets. Both GPUs are end-of-life products, and neither supports ray tracing or tensor cores, so modern gaming features are absent from both. The final call depends on whether the workload is compute-limited (choose the 825M) or memory-limited (choose the GT 645M).