Buying High-Speed Cables: 5 Specs You Must Check

When you're building or upgrading systems with SAS 4.0, PCIe Gen 4.0, or Gen 5.0, the cable you choose isn't just a connector — it's a critical part of your system’s performance. One wrong spec can lead to signal loss, failed links, or underperforming drives.

Here are 5 specs you absolutely need to check before buying high-speed internal or external cables.

1. Connector Type (SFF-xxxx)

Always confirm the SFF number for both ends of the cable. Confusing SFF-8644 (external HD MiniSAS) with SFF-8643 (internal) or SFF-8654 (SlimSAS) is one of the most common buying mistakes.

Examples:

• SFF-8654 (SlimSAS) = internal PCIe/SAS
• SFF-8644 (HD MiniSAS) = external SAS
• SFF-8639 = U.2 NVMe
• SFF-8087 = legacy MiniSAS

Get the numbers right, or nothing connects.

2. Protocol Support: SAS vs PCIe

Many connectors look identical but carry different signals.

• A SlimSAS cable wired for PCIe Gen 4.0 won’t work if your target uses SAS signaling
• Cables like SlimSAS 8i to 2x U.2 are PCIe only
• Breakouts to SATA or SAS drives need SAS signaling support

Double-check that the cable supports your protocol—not just the connector type.

3. Lane Count (x4, x8, etc.)

High-speed cables typically carry 4 or 8 lanes of data. The lane count affects bandwidth and compatibility with controllers and backplanes.

For example:

• SlimSAS 4i = 4 lanes
• SlimSAS 8i = 8 lanes
• Breakouts should match the controller’s lane distribution

Mismatching lanes can cause performance bottlenecks—or total failures.

4. Data Rate / Bandwidth Rating

Make sure the cable supports your target speed:

• SAS 3.0 = 12Gb/s per lane
• SAS 4.0 = 24Gb/s per lane
• PCIe Gen 4.0 = 16GT/s per lane
• PCIe Gen 5.0 = 32GT/s per lane

Look for high-speed assemblies tested to meet or exceed the spec you need.

5. Cable Length and Signal Integrity

Longer cables lose signal strength—especially at high frequencies. The higher the speed, the shorter your cable should be to preserve signal integrity.

Use:

• Shortest practical length
• Shielded, low-loss construction
• High-quality assemblies built for Gen 4/5 environments

If your setup requires longer runs, consider Active Optical Cables (AOC) instead of copper.

Buying With Confidence

At Data Storage Cables, we help engineers and IT teams avoid costly mistakes. Every cable we build or stock is specified by SFF number, protocol, lane count, and speed rating, so you get exactly what your system needs.