Upgrading Your Current System to USB 3.0
If you want to add USB 3.0 devices to your system and get the performance and other benefits they provide, you first need to add USB 3.0 ports to your system.
Add-on Card for Desktop Computers
Adding USB 3.0 ports via an add-on card is easier and less expensive than replacing the motherboard or purchasing a new computer. To upgrade a desktop computer to USB 3.0, you must have an available PCI Express (PCIe) slot that’s x1 or wider.
PCIe x4 cards that provide both USB 3.0 and eSATA 6GBps are currently available from ASUS, but others may become available over time.
Checking the Fine Print
Be sure to check the following issues when you compare these cards:
Bracket types providedIf you are planning to install a USB 3.0 card into a system that uses shorter-than-normal card brackets (such as a low-profile or home theater PC), make sure you choose a card that includes a low-profile bracket.
Auxiliary power requirementsSome cards use a four-pin hard disk (Molex) power connector, while others use a four-pin floppy power connector, an SATA power connector, or a USB motherboard header. Depending upon your power supply or motherboard design and drives in use, you might need to use an adapter or a splitter to deliver power to your card.
Version of PCIe supportedTo get the maximum level of USB 3.0 performance, make sure your card supports PCIe version 2.0 or greater. PCIe version 2.0 supports twice the bandwidth of PCIe version 1.0, and most recent motherboards support PCIe version 2.0 (check your motherboard/system documentation if you’re not sure).
PCIe x1 versus x4Almost all of the PCIe cards for USB 3.0 use the x1 expansion slot, which means they can fit into x1 or wider PCIe slots (x4, x8, x16). Thus, they can be used in any PCIe motherboard. Unfortunately, a PCIe x1 slot cannot provide full performance for even a single USB 3.0 port.
Differences Between PCIe x1 and x4
Wondering why your PCIe x1 slots are useless for USB 3.0?
- The bandwidth of a PCIe x1 slot is 250MBps in version 1; most recent motherboards support PCIe version 2, which doubles each lane to 500MBps.
- A single USB 3.0 port has a bandwidth of 600MBps.
- Consequently, a single USB 3.0 device saturates the bandwidth of a PCIe x1 v2.0 slot, and two USB 3.0 devices (all USB 3.0 PCIe cards have two ports) receive only 250MBps each on a system running PCIe version 2 slots and a PCIe version 2 USB 3.0 card, and just half that if running on PCIe version 1 hardware.
ASUS’s U36S card works around these limitations by using a PLX bridge chip to support the PCIe x4 expansion slot’s additional lanes over x1.
These factors appear to make a PCIe x4 USB 3.0 card which also offers a couple of eSATA 6Gbps ports more attractive from a performance and feature standpoint. However, there’s still more ‘fine print’ to consider before you decide to get one:
- Does your computer have any available PCIe x4 or wider slots? Many do not. Although you can use a PCIe x16 slot for the card, using an x16 slot might prevent your being able to run SLI or CrossFire dual graphics cards, especially on a motherboard using an Intel chipset. Note that some new motherboards use the x16 form factor for slots that have x8 or x4 connectors. Review the motherboard’s documentation to see the actual PCIe lanes supported in each slot.
- Is your computer/motherboard compatible with the card you want to use? For example, the ASUS U3S6 card is recommended for certain ASUS motherboards only (see the “Compatible Models” list at the link). If you want to get this card to work on other motherboards, be prepared to make configuration changes to your system, as listed in some of the feedback at the Newegg website and elsewhere.
- Does your motherboard have enough PCIe lanes to support the card and other PCIe devices you have installed (such as a second PCIe x16 card for SLI or Crossfire)? Some motherboards feature PCI Express 2.0.0 lanes mainly for graphics and PCIe v1.0 lanes (which run at half the speed of v2.0) for I/O cards. If you use dual graphics cards (NVIDIA SLI or ATI/AMD Crossfire), the motherboard must use the PCIe v1.0 lanes for your card, reducing performance (see this detailed performance review at Anandtech for more information).
- If you plan to use the SATA 6Gbps interface, do you really need it? The only drives currently on the market that require the full performance of SATA 6Gbps are some late-model SSDs. If you’re running mechanical hard disks, SATA 3Gbps is more than fast enough for now.