NICs & Optics
Summary
The lab uses three 10GbE NICs and a mix of SFP+ SR transceivers, a 10GBASE-T transceiver, and OM3 fiber to connect workstations to the CRS305 media switch. The primary NICs are two Mellanox ConnectX-3 MCX311A-XCAT (single-port SFP+, 46 from Amazon) is used in Stream-PC because it’s the only 10GbE card that fits the available PCIe x1 slot (after removing the Sound Blaster Audigy Fx).
The fiber path uses two qsfptek 10G SFP+ SR 850nm transceivers (6.99). This links SERVER-PC in the network rack to CRS305 in the studio. Stream-PC connects via a short Cat6 cable through an osfptek 10GBASE-T SFP+ transceiver (already owned) in CRS305 port 2.
Timeline
- 2026-04-03: NIC placement plan determined based on available PCIe slots.
- 2026-04-03: Sound Blaster Audigy Fx removed from Stream-PC to free PCIe x1 slot.
- 2026-04-03: All NICs, transceivers, and fiber ordered.
Current State
All ordered, pending delivery. NIC placement plan:
| NIC | PC | Slot | Connection |
|---|---|---|---|
| ConnectX-3 #1 | SERVER-PC | PCIe x4 (freed USB card slot) | SFP+ SR → 10m OM3 fiber → CRS305 p1 |
| ConnectX-3 #2 | Game-PC (future) | PCIe x16 (open slot on X670E Taichi) | SFP+ DAC → CRS305 p3 |
| RTL8127 | Stream-PC | PCIe x1 (freed Sound Blaster slot) | RJ45 → Cat6 → 10GBASE-T SFP+ → CRS305 p2 |
Key Decisions
- 2026-04-03: ConnectX-3 over Intel X520 — PTP hardware timestamping support is the deciding factor.
- 2026-04-03: RTL8127 for Stream-PC — only PCIe x1 slot available. ConnectX-3 needs x4 minimum.
- 2026-04-03: SFP+ SR + fiber over DAC for SERVER-PC — 10m distance between rack and studio requires fiber.
- 2026-04-03: Sound Blaster removed — audio rerouted through motherboard Realtek USB2.0 to Focusrite 18i20 analog 5-6.
Experiments & Results
| Experiment | Status | Finding | Source |
|---|---|---|---|
| ConnectX-3 HW timestamping in WSL2 | Planned | Likely not supported — need VM passthrough | Phase 1 plan |
| RTL8127 link speed through 10GBASE-T SFP+ | Planned | Expect 10Gbps | Hardware inventory |
| OM3 fiber 10m link integrity | Planned | Should be trivial at this distance | Hardware inventory |
Gotchas & Known Issues
- WSL2 can’t see physical NICs — no hardware timestamping via WSL2. Need Linux VM with PCIe passthrough.
- 10GBASE-T SFP+ transceivers run hot — the osfptek module in CRS305 needs airflow monitoring.
- Stream-PC has only x1 PCIe — ConnectX-3 physically won’t fit. RTL8127 is the only option.
- Mellanox WinOF driver may be needed — ConnectX-3 might not be auto-detected on Windows.
Open Questions
- Will the ConnectX-3 need firmware updates for PTP support?
- Does the RTL8127 support any form of hardware timestamping?
- What’s the actual power draw of the 10GBASE-T SFP+ transceiver in the CRS305?