Add Dell R720/R730 installation guide for dual RTX 5000 + NVLink
Complete shopping list with Dell-specific part numbers: - GPU power cables: 9H6FV / N08NH (~$10-15 each, need 2) - GPU Riser 3 required for second GPU slot - Low-profile heatsinks needed on R720 (usually pre-installed on R730) - 2x 1100W PSUs mandatory, non-redundant mode for full wattage Documents riser layout, NVLink bridge clearance in 2U, potential issues (CPU TDP limits, "unsupported" GPU warning, blower noise), and R720 vs R730 comparison. Total build cost ~$940-960 with Dell parts. https://claude.ai/code/session_01PtYTPherSJaxDEVPgF6Nxu
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Claude
@@ -320,12 +320,110 @@ watch -n 0.5 nvidia-smi
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**Phase 2 — Add second card + NVLink ($450)**
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1. Buy matching Quadro RTX 5000 — ~$400
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2. Buy NVLink HB Bridge 3-slot (part: P4934 / 1JF3K / 6FY12AA) — ~$50
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2. Buy NVLink HB Bridge 2-slot (part: P4934 / 1JF3K / 6FY12AA) — ~$50
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3. Install second card in adjacent/nearby x16 slot
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4. Connect NVLink bridge
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5. Verify with `nvidia-smi nvlink --status`
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6. Now running 32GB unified — Qwen3.5-35B-A3B at Q4_K_M with full 262K context
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### Dell R720/R730 Installation Guide
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#### Prerequisites (MUST HAVE before buying GPUs)
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| Requirement | R720 | R730 | Why |
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|-------------|-------|-------|-----|
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| **Dual CPUs** | Required | Required | GPU riser slots are wired to CPU2 — dead without it |
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| **2x 1100W PSUs** | Required | Required | 2x 230W GPUs + system = ~600W+ under load |
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| **GPU Riser 3** | Required for 2nd GPU | Required for GPUs | Provides the PCIe x16 slot + 8-pin power |
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| **GPU Power Cable** | Required | Required | Riser-to-GPU power, not included by default |
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| **Low-Profile Heatsinks** | Must swap (part of enablement kit) | Usually pre-installed | Standard heatsinks block GPU riser clearance |
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| **Max ambient temp** | 30°C (not the usual 35°C) | 30°C | High GPU TDP restricts cooling headroom |
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#### Shopping List: Dell-Specific Parts
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| Part | Dell P/N | What It Is | Price | Where |
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|------|----------|------------|-------|-------|
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| **GPU Power Cable** | **9H6FV** (09H6FV) | 8-pin EPS (riser) → 6-pin + 6+2-pin PCIe. One cable powers one GPU | ~$10-15 | Amazon, eBay |
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| **GPU Power Cable (alt)** | **N08NH** (0N08NH) | Same function, alternate Dell part number | ~$10-15 | Amazon, eBay |
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| **GPU Riser 3** (R720) | Check eBay for "R720 riser 3" or "R720 GPU riser" | Second riser card that provides GPU-capable x16 slot | ~$15-30 | eBay |
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| **GPU Riser 3** (R730) | Check eBay for "R730 riser 3" or "R730 GPU riser" | R730 version — NOT interchangeable with R720 | ~$15-30 | eBay |
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| **Low-Profile Heatsinks** (R720 only) | Part of original GPU enablement kit | Shorter heatsinks that clear the GPU riser. Search "R720 low profile heatsink" | ~$10-20/pair | eBay |
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**You need 2x power cables** (one per GPU). Search Amazon for "Dell R720 R730 GPU power cable 9H6FV" — multiple sellers (COMeap, ZAHARA, BestParts) stock them for ~$10-15 each.
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#### How It Fits
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```
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Dell R720/R730 Riser Layout (rear view):
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┌─────────────────────────────────────┐
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│ Riser 1 Riser 2 Riser 3│
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│ (network/ (GPU 1) (GPU 2)│
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│ storage) PCIe x16 PCIe x16│
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│ Gen2(720) Gen2(720)│
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│ Gen3(730) Gen3(730)│
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└─────────────────────────────────────┘
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↑ RTX 5000 ↑ ↑ RTX 5000 ↑
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└── NVLink Bridge ──┘
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```
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- Both GPUs sit on **adjacent risers** (Riser 2 + Riser 3) — this is 2-slot spacing
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- The **2-slot NVLink bridge** (P4934) is the correct size for R720/R730
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- The cards mount **vertically** via risers, parallel to each other
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- NVLink bridge connects across the top of both cards
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#### R720 vs R730
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| Feature | R720 | R730 |
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|---------|------|------|
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| **PCIe** | Gen2 x16 | **Gen3 x16** |
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| **Impact on LLM** | None — VRAM-bound | None — VRAM-bound |
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| **Impact on NVLink** | None — NVLink bypasses PCIe | None — NVLink bypasses PCIe |
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| **GPU power delivery** | Same 8-pin from riser | Same 8-pin from riser |
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| **Heatsink swap** | Usually required | Usually already low-profile |
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| **Used price** | ~$100-150 cheaper | Preferred if budget allows |
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| **Recommendation** | Fine if you already have one | **Buy this one** if shopping new |
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#### Potential Issues
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1. **NVLink bridge clearance in 2U** — The bridge sits on top of both GPUs. In a 2U chassis
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this is tight. The R720/R730 riser design mounts cards vertically which actually helps —
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the bridge faces the chassis side panel, not the lid. Should fit, but measure before buying.
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2. **Blower fan noise** — The RTX 5000 has an active blower (unlike passive Tesla cards).
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The server's own fans may spin higher to compensate. The blower exhausts out the bracket
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which is correct for rack airflow.
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3. **"Unsupported" GPU warning** — Dell officially supports Tesla/Quadro cards from their era.
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The Quadro RTX 5000 is a later generation than R720/R730 was designed for, but community
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reports confirm Quadro RTX and even consumer RTX cards work fine. You won't get Dell support
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if something goes wrong, but electrically it's standard PCIe.
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4. **CPU TDP limit** — Dell requires CPUs of 115W or less when GPUs are installed (R720).
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Check your CPU model. Most common Xeon E5-2600 v1/v2 (R720) and E5-2600 v3/v4 (R730)
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processors are within this range, but some high-core-count variants exceed it.
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5. **PSU mode** — With dual 300W GPUs, set PSU configuration to **non-redundant mode**
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to use combined wattage from both PSUs. In redundant mode, you're limited to one PSU's
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capacity (1100W) which may not be enough under full GPU + CPU load.
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#### Complete R720/R730 Shopping List
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```
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GPUS + NVLINK
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2x Quadro RTX 5000 ~$800
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1x NVLink Bridge 2-slot (P4934 / L55997-001) ~$50
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DELL-SPECIFIC PARTS
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2x GPU Power Cable (9H6FV or N08NH) ~$25
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1x GPU Riser 3 (match your server model!) ~$20
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2x Low-Profile Heatsinks (R720 only) ~$15
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POWER (if not already installed)
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2x Dell 1100W PSU ~$30-50 ea
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TOTAL (assuming you have the server + dual CPUs) ~$940-960
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```
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## 24GB GPU Options (Previous Research — Still Valid for Tighter Budgets)
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| GPU | VRAM | Price Range | Best Deals | Notes |
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