| Model & Quantization | VRAM Demand | NVIDIA GeForce RTX 3090 | NVIDIA GeForce RTX 5080 |
|---|---|---|---|
| Alibaba Qwen3-Coder 30B-A3B (Q4_K_M) | 20.66 GB | Resident (+3.34 GB, >100 tok/s) | Exceeds VRAM (-4.66 GB Swap) |
| Qwen 2.5 Coder 32B (Q4_K_M) | 23.10 GB | Fits Tight (+0.90 GB, ~35 tok/s) | Exceeds VRAM (-7.10 GB OOM) |
| Mistral Small 24B (Q4_K_M) | 17.82 GB | Comfort Margin (+6.18 GB) | Exceeds VRAM (-1.82 GB OOM) |
| Tencent HunyuanVideo 13B (Q4 / NF4) | 16.41 GB | Comfort Margin (+7.59 GB) | Overflow (-0.41 GB Tight Offload) |
| Qwen 2.5 14B Instruct (Q4_K_M, 32k FP8) | 14.06 GB | Comfort Margin (+9.94 GB) | Tight Fit (+1.94 GB, ~80 tok/s) |
Raw bandwidth parity exposes the glaring asymmetry in this $419 price gap. Ampere GA102 achieves 936 GB/s by ganging twelve 32-bit channels into a 384-bit GDDR6X bus, almost equaling the 960 GB/s produced by GB203's 30 Gbps GDDR7 over a narrower 256-bit interface. Where the RTX 5080 genuinely pulls ahead is tensor math density: Blackwell's 5th-generation Tensor Cores execute hardware FP8 and MXFP4/NVFP4 matrix instructions that GA102 lacks, accelerating prompt time-to-first-token on long coding contexts by over 2.5x and trimming ComfyUI FLUX denoising times. Furthermore, the 5080 includes PCIe 5.0 x16 host lanes and dual 9th-gen NVENC hardware encoders. Yet whenever a checkpoint breaches 16 GB—including Qwen3-Coder 30B-A3B (20.66 GB) or Mistral Small 24B (17.82 GB)—that generational Tensor Core advantage vanishes across slow PCIe memory transfers.
Stuck on a 16GB RTX 5080 and unwilling to downgrade below 24B parameter models? Launch `llama-server` with `-fa on -ctk q8_0 -ctv q8_0` and load `Mistral-Small-24B-IQ3_M` (`~14.5 GB`), or selectively offload cold Mixture-of-Experts weights via `--n-cpu-moe` instead of suffering 2 tok/s full-layer DDR5 memory swapping.
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On models under 14B parameters, prompt prefill feels snappier on the RTX 5080, while steady-state token streaming (80 vs 78 tok/s) is indistinguishable. On 24B–32B models, the RTX 3090 is 15x faster because weights stay in VRAM.
Older ATX 2.4 750W power supplies risk sudden OCP shutdowns during 500W+ millisecond Ampere or Blackwell prefill transients. Upgrading to a modern 1000W ATX 3.1 unit with a native 12V-2x6 rail absorbs spikes cleanly and preserves headroom for a second GPU.
Inspect exact KV-cache formulas, test 32k/128k context allocations, or compare cloud rental break-even costs in the interactive matchmaker.
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