What does dual-slot mean?
Dual-slot describes how wide an expansion card is. A dual-slot card, almost always a graphics card, has a heatsink and fans thick enough to take up the space of two expansion slots. It plugs into one PCIe slot, usually the x16 slot, but its bracket covers two openings on the back of the case and its cooler hangs over the slot next to it.
Slot widths compared
| Width | What it means | Typical cards |
|---|---|---|
| Single-slot | One bracket opening; the card fits in one slot's space | NICs, sound cards, some entry-level and workstation graphics cards |
| Dual-slot | Two bracket openings; the cooler covers the neighboring slot | Many mid-range and high-end graphics cards |
| 2.5-slot, 3-slot and wider | The cooler blocks two or more neighboring slots | Large high-end graphics cards |
| Low-profile | A shorter bracket for slim cases; this is height, not width | Small form factor PC cards |
Width and height are separate: a low-profile graphics card can still be dual-slot.
Fit checks before you install
- The slot next to it: in a standard tower the cooler covers the slot below the card, which usually becomes unusable. Plan where other cards go.
- Case openings: the case needs two free rear bracket openings lined up with the slot. Small cases may have only two in total.
- Length and height: check the card's length against drive cages and front fans, and its height against the side panel, including room for the power cables to bend.
- Airflow: the card's fans need space to pull in air. A card packed tight against another card or a PSU shroud runs hotter.
- Power and support: larger cards usually need PCIe auxiliary power connectors and may include a support bracket to stop sag.
Dual-slot vs. dual graphics cards
Dual-slot is about one card's physical width. It isn't the same as running two graphics cards, or a board having two x16 slots. If you do install two dual-slot cards, the board's slots must be spaced far enough apart and the case needs four free bracket openings.
For the CompTIA A+ exam
Core 1 (220-1201) objective 3.5 covers installing expansion cards, including video cards, along with motherboard form factors. Slot width isn't named in the objectives, but in a build scenario check three things for a video card: slot width (single or dual), bracket height (full-height or low-profile) and length.