PCI & PCIe Riser Cards

22nd Thursday, 2012  |  Engineering News, Life at LAVA  |  no comments

In a server room, space is at a premium. As a consequence, the hardware is placed in racks of a standardized width and height, with a standardized spacing between mounting points along the racks’ vertical mounting rails. What has evolved are computers designed with correspondingly specific heights and width/s, to fit this storage and mounting system. The basic unit of height (called a “u”), is 1.75 inches vertically, and a standard rack is 42u high, just over 6 feet. Logically enough, a 2u height is 3.5 inches vertically, and so on; and a 1u server is, as its name indicates, 1u high.

42u server rack

So a 1u server is a computer 19 inches wide and 1.75 inches high (allowing for a small space between units vertically and mounting “ears” on the sides): in other words, pretty flat and skinny. A 2u server is the same width, but twice the height.

In the cases of both 1u and 2u servers however, their vertical height is less than the vertical height of conventional PCI adapter cards, which began their life in the spacious desktop computers of the 1980s.

 

2u rackmount server
So how do you fit a 4.2 inch high PCI or PCIe card into a 3 inch high space? Or for that matter, into a 1.75 inch high space? The answer is simple: turn it on its side, using a riser card.

Riser cards

Riser cards

Riser cards are relatively simple both mechanically and electrically: mechanically, they plug into a slot on a motherboard, and rise just a short distance before they present a connector (or two or three) to the horizontal plane. Electrically, they reproduce the slots they plug into The adapter cards now plug in horizontally, an the height problem is solved.

Riser card in server

Riser card in server

LAVA manufactures many PCI and PCI Express (PCIe) cards for this hardware environment.