GPU comparison
RTX 3090 vs RTX 4090 for Local LLM
Draft comparison for future runtime-specific local LLM testing.
Planning summary only. Verify exact GPU variants, runtime support, and workload behavior before making purchase decisions.
RTX 3090
- VRAM
- 24 GB
- Memory type
- GDDR6X
- Bandwidth
- 936.2 GB/s
- Board power / TGP
- 350 W
RTX 4090
- VRAM
- 24 GB
- Memory type
- GDDR6X
- Bandwidth
- 1008 GB/s
- Board power / TGP
- 450 W
Quick planning summary
RTX 3090: 24 GB | RTX 4090: 24 GB
RTX 3090: 936.2 GB/s | RTX 4090: 1008 GB/s
RTX 3090: 350 W | RTX 4090: 450 W
Local LLM planning
RTX 3090: medium | RTX 4090: medium
Benchmark evidence, exact board-partner variant, runtime compatibility, and workload fit.
Comparison table
| Field | RTX 3090 | RTX 4090 |
|---|---|---|
| Memory planning | ||
| VRAM | 24 GB | 24 GB |
| Memory type | GDDR6X | GDDR6X |
| Memory bus | 384-bit | 384-bit |
| Memory bandwidth | 936.2 GB/s | 1008 GB/s |
| Compute / architecture | ||
| Vendor | NVIDIA | NVIDIA |
| Architecture | Ampere | Ada Lovelace |
| Core / execution units | 10496 CUDA cores | 16384 CUDA cores |
| Power planning | ||
| Board power / TGP | 350 W | 450 W |
| Power connector | Needs verification | 1 x PCIe Gen5 (or 3 x 8-pin adapter) |
| Verification | ||
| Status | Source-backed GPU specs available | Source-backed GPU specs available |
| Data confidence | medium | medium |
| Last verified | 2026-05-29 | 2026-05-29 |
Cautious verdict
RTX 4090 has higher listed memory bandwidth than RTX 3090. RTX 3090 has the lower listed power planning figure.
This is not a benchmark verdict, and it should not be treated as purchase guidance.
Final fit still depends on model size, quantization, runtime support, drivers, and tested workload behavior.
How to interpret this comparison
VRAM is capacity headroom, not guaranteed speed. Memory bandwidth can matter, but benchmark evidence is still needed before drawing performance conclusions.
Runtime support, drivers, and exact board-partner variants can change practical results. Use the VRAM Calculator before treating this comparison as purchase guidance.
RECOMMENDED NEXT STEP
Check model memory before choosing between these GPUs
Run your model assumptions through the VRAM Calculator, then return to GPU profiles for source notes and board-partner verification.
Use case notes
For local LLM planning, prioritize VRAM headroom and runtime compatibility. For image workflows, avoid assuming performance until benchmark evidence is attached.
When to choose cloud GPU instead
Consider cloud testing when memory estimates exceed local cards, when workloads are infrequent, or when validating before hardware purchase.
FAQ
Why compare two 24 GB NVIDIA GPUs for local LLM planning?
Both profiles can fit into a high-VRAM shortlist, so the planning question shifts toward memory bandwidth, power, architecture, and tested runtime behavior rather than capacity alone.
When should I use the VRAM Calculator first?
Use it before comparing cards so your shortlist matches estimated memory requirements.
When should I choose cloud GPU instead?
When local VRAM is below estimate, testing is occasional, or you need validation before buying.
Should I rely on this comparison as purchase guidance?
No. This page is planning guidance and intentionally avoids unsupported benchmark, price, availability, and buying claims.
Related GPU profiles
Sources and data confidence
RTX 3090
Confidence: medium
Source types: official, database
RTX 4090
Confidence: medium
Source types: official, paper
No benchmark source is attached to this comparison, so benchmark claims are not included.