NVIDIA GeForce GT 645M vs NVIDIA Quadro K3100M Comparison

Where Each One Wins

The NVIDIA Quadro K3100M takes the overall win count, capturing two of the three recorded head-to-head benchmarks. Its victories come in compute-oriented workloads, where the K3100M's larger silicon and wider memory interface deliver decisive margins. The GeForce GT 645M, by contrast, claims a single but substantial win in the Metal graphics API test, where it outperforms the K3100M by a wide margin. This creates a clear split: the Quadro K3100M is the stronger choice for OpenCL compute and Vulkan-based workloads, while the GeForce GT 645M leads in Metal-specific tasks.

The data shows that the K3100M's average benchmark score of 5154 places it in the 30th percentile of all GPUs, while the GT 645M's average of 4411 sits in the 26th percentile. That 743-point gap in average score, roughly a 16.8% advantage for the Quadro, reflects the K3100M's dominance in two of the three tests. However, the GT 645M's Metal score is not a minor outlier; it is a full 48.5% higher than the Quadro's Metal result, making that workload the single largest swing in either direction.

For users prioritizing compute throughput, the K3100M is the obvious pick. Its OpenCL score of 6154 is more than double the GT 645M's 2680, a 129.6% delta that dwarfs every other comparison in the data. In Vulkan, the K3100M again leads, scoring 5484 against 4875, a 12.5% advantage. The GT 645M, conversely, is the dedicated choice for Metal environments, where its 5679 score outstrips the K3100M's 3823 by 32.7%.

Architecture Differences

Both GPUs are built on NVIDIA's Kepler architecture and use TSMC's 28 nm process node, but they diverge sharply in scale and configuration. The Quadro K3100M uses the GK104 chip, which packs 3,540 million transistors on a 294 mm² die, giving a transistor density of 12.0 million per square millimeter. The GeForce GT 645M uses the smaller GK107 chip, with 1,270 million transistors on a 118 mm² die, a density of 10.8 million per square millimeter. That is nearly three times the transistor count and more than double the die area for the K3100M.

The compute resources scale accordingly. The K3100M features 768 shading units, 64 texture mapping units, and 32 ROPs. The GT 645M is halved in each category, with 384 shading units, 32 TMUs, and 16 ROPs. This doubling of execution resources explains the K3100M's commanding lead in raw throughput metrics: its pixel rate is 11.30 GPixel/s versus 6.240 GPixel/s, and its texture rate is 45.18 GTexel/s versus 24.96 GTexel/s. FP32 performance tells a similar story, with the K3100M delivering 1,084.4 GFLOPS against the GT 645M's 599.0 GFLOPS.

Memory architecture also differs fundamentally. The K3100M comes with 4 GB of GDDR5 on a 256-bit bus, yielding 102.4 GB/s of bandwidth. The GT 645M has 2 GB of DDR3 on a 128-bit bus, for just 28.80 GB/s. That is a 3.6x bandwidth advantage for the Quadro, a gap that heavily influences its OpenCL and Vulkan results. Clock speeds are closer: the K3100M runs at 706 MHz base and boost, while the GT 645M runs at 709 MHz base and boosts to 780 MHz. Memory clocks also differ, with the K3100M at 800 MHz (3.2 Gbps effective) and the GT 645M at 900 MHz (1800 Mbps effective), but the bus width difference overwhelms the clock advantage.

Power and form factor diverge as well. The K3100M is rated at 75 W TDP and uses an MXM-B (3.0) interface, while the GT 645M is a 32 W part integrated as an IGP with a PCIe 3.0 x16 bus interface. Both are end-of-life products, with the K3100M released in July 2013 as part of the Quadro Kepler-M (Kx100M) generation, and the GT 645M released in September 2012 in the GeForce 600M line. The K3100M's predecessor is Quadro Fermi-M and its successor is Quadro Maxwell-M, while the GT 645M follows GeForce 500M and precedes GeForce 700M.

Head-to-Head Benchmarks

The three recorded benchmarks reveal a polarized performance profile. In OpenCL, the Quadro K3100M scores 6154 against the GT 645M's 2680. That is a 129.6% delta, meaning the K3100M more than doubles the GT 645M's compute output. No other comparison in the data approaches this margin. The K3100M's 768 shading units, 64 TMUs, and 102.4 GB/s of memory bandwidth all feed this result, making it a dominant compute part.

In Vulkan, the K3100M again wins, scoring 5484 versus 4875, a 12.5% delta. This is a more moderate victory, but it still places the Quadro clearly ahead in modern graphics API workloads. The K3100M's higher pixel and texture rates likely contribute here, as does its larger memory pool.

The GT 645M's sole victory comes in Metal, where it scores 5679 against the K3100M's 3823. The delta is -32.7% from the K3100M's perspective, meaning the GT 645M is 32.7% ahead. This is a striking reversal given the Quadro's hardware advantage, and it suggests that Metal workloads favor the GT 645M's specific configuration, possibly its higher boost clock of 780 MHz or its driver optimization profile. The result is not close: the GT 645M's Metal score is 48.5% higher than the Quadro's, making it the largest per-test gap in the entire dataset after OpenCL.

Averaging across all three tests, the K3100M's mean of 5154 versus the GT 645M's 4411 gives the Quadro a 16.8% overall advantage. Yet the distribution of wins matters more than the average. For OpenCL-heavy workflows, the K3100M is untouchable. For Metal-only pipelines, the GT 645M is the clear leader. Vulkan sits in the middle, with the K3100M ahead but not overwhelmingly so.

FAQ

Q: Which GPU has the higher average benchmark score?

A: The NVIDIA Quadro K3100M, with an average score of 5154 compared to the GeForce GT 645M's 4411, a difference of 743 points.

Q: How much faster is the Quadro K3100M in OpenCL?

A: The K3100M scores 6154 in OpenCL versus 2680 for the GT 645M, a 129.6% delta, meaning it is more than twice as fast.

Q: In which benchmark does the GeForce GT 645M win?

A: The GT 645M wins in the geekbench_metal test, scoring 5679 against the K3100M's 3823, a 32.7% advantage.

Q: What is the bandwidth difference between the two GPUs?

A: The K3100M has 102.4 GB/s of bandwidth from its 256-bit GDDR5 memory, while the GT 645M has 28.80 GB/s from its 128-bit DDR3 memory.

Q: How do their shading unit counts compare?

A: The K3100M has 768 shading units, exactly double the GT 645M's 384 shading units.

Q: What are their transistor counts?

A: The K3100M uses 3,540 million transistors on a 294 mm² die, while the GT 645M uses 1,270 million transistors on a 118 mm² die.

Specification Differences

| Specification | NVIDIA Quadro K3100M | NVIDIA GeForce GT 645M |

|---|---|---|

| Chip | GK104 | GK107 |

| Generation | Quadro Kepler-M (Kx100M) | GeForce 600M |

| Transistors | 3,540 million | 1,270 million |

| Die Size | 294 mm² | 118 mm² |

| Transistor Density | 12.0M / mm² | 10.8M / mm² |

| Base Clock | 706 MHz | 709 MHz |

| Boost Clock | 706 MHz | 780 MHz |

| Memory Clock | 800 MHz, 3.2 Gbps effective | 900 MHz, 1800 Mbps effective |

| Memory Size | 4 GB | 2 GB |

| Memory Type | GDDR5 | DDR3 |

| Memory Bus Width | 256 bit | 128 bit |

| Memory Bandwidth | 102.4 GB/s | 28.80 GB/s |

| Shading Units | 768 | 384 |

| TMUs | 64 | 32 |

| ROPs | 32 | 16 |

| Pixel Rate | 11.30 GPixel/s | 6.240 GPixel/s |

| Texture Rate | 45.18 GTexel/s | 24.96 GTexel/s |

| FP32 Performance | 1,084.4 GFLOPS | 599.0 GFLOPS |

| TDP | 75 W | 32 W |

| Slot Width | MXM Module | IGP |

| Bus Interface | MXM-B (3.0) | PCIe 3.0 x16 |

| Release Date | 2013-07-22 | 2012-09-30 |

| Predecessor | Quadro Fermi-M | GeForce 500M |

| Successor | Quadro Maxwell-M | GeForce 700M |

The Verdict

The data points to a clear split based on workload. The NVIDIA Quadro K3100M is the superior compute and Vulkan GPU, winning two of three benchmarks and holding a 16.8% average score advantage. Its 129.6% OpenCL lead is the defining metric: for any task that leverages OpenCL, the K3100M is the only rational choice. Its 12.5% Vulkan win further cements its position for modern cross-platform graphics. The Quadro's 4 GB GDDR5 memory and 102.4 GB/s bandwidth give it a structural advantage that the GT 645M cannot overcome in these workloads.

The NVIDIA GeForce GT 645M is the pick for Metal-specific applications. Its 5679 Metal score is 32.7% higher than the K3100M's, a margin large enough to justify choosing it despite losing the other two tests. The GT 645M also draws far less power at 32 W versus 75 W, which matters for thermally constrained systems. Its smaller die and lower transistor count make it a lighter part, but its Metal performance shows that raw hardware scale is not the only factor.

For users who need a balanced mobile GPU with compute strength, the K3100M is the verdict. For those whose primary API is Metal, the GT 645M wins outright. The choice is not about which GPU is generally better, it is about which benchmark matters most in the target environment. The database records show no ambiguity: OpenCL and Vulkan belong to the Quadro, Metal belongs to the GeForce.