Adrive bay is a standard-sized area for addinghardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed.
Over the years since the introduction of theIBM PC, it andits compatibles have had many form factors of drive bays. Four form factors are in common use today, the 5.25-inch, 3.5-inch, 2.5-inch or 1.8-inch drive bays. These names do not refer to the width of the bay itself, but rather to the width of the disks used by the drives mounted in these bays.
8.0-inch drive bays were found in earlyIBM computers,CP/M computers, and theTRS-80 Model II. They were4+5⁄8 inches (117.5 mm) high,9+1⁄2 inches (241.3 mm) wide, and approximately14+1⁄4 inches (361.9 mm) deep, and were used forhard disk drives andfloppy disk drives. Thisform factor is obsolete. Later models of floppy drives like the Shugart SA810 HH from 1982 were 12 inches deep and 2 inches high and didn’t require any AC power too.
5.25-inch drive bays are divided into two height specifications,full-height andhalf-height.
Full-height bays were found in oldPCs in the early to mid-1980s. They were3+1⁄4 inches (82.6 mm) high,5+3⁄4 inches (146.1 mm) wide, and up to 8 inches (203.2 mm) deep, used mainly for hard disk drives and floppy disk drives. This is the size of the internal (screwed) part of the bay, as the front side is actually5+7⁄8 inches (149.2 mm). The difference between those widths and the name of the bay size is because it is named after the size of floppy that would fit in those drives, a 5.25-inch-wide square.
Half-height drive bays are1+5⁄8 inches (41.3 mm) high by5+3⁄4 inches (146.1 mm) wide, and are the standard housing forCD andDVD drives in modern desktop computers (newer models are usually 7" deep, any deeper is for older or specific high performance models). This form factor originally appeared in the earlyPC AT era and was at that time used for 5.25-inch floppy disk drives and the hard disk drives of the time (roughly between 10 and 100 MB). As the name indicates, two half-height devices can fit in one full-height bay. Some 5.25 floppy drives are also shorter at 6.5-7.5 inches but this was quite rare.
Both full-height and half-height 5.25-inch bays were typically designed with a case opening at the front of the bay, needed for removable media, but also normally used by 5.25-inch hard disk drives for a front panel with a drive activity LED.
The dimensions of a 5.25-inch floppy drive are specified in theSFF standard specifications which were incorporated into the EIA-741 "Specification for Small Form Factor 133.35 mm (5.25 in) Disk Drives" by the Electronic Industries Association (EIA).[1] Dimensions of5.25 optical drives are specified in the SFF standard (they are somewhat shorter and not only size of the body is standardized, but also size of the bezel).
3.5-inch bays, like their larger counterparts, are named after diskette dimensions; the current dimensions, originally known as "slim height" is 4 inches (101.6 mm) wide by 1.028 inches (26.1 mm) high. The original "full-height" 3.5-inch hard drives and their drive bays were1+5⁄8 inches (41.3 mm) high, the same as half-height 5.25" units. Bays with an opening in the front of the case are generally used forfloppy orZip drives (now obsolete), but early hard disks used such bays too and had a front panel with an activity LED just like floppy drives. Modern hard drives do not have a front panel a and are mounted in fully internal 3.5" bays without a front opening. Modern computers do not come with a floppy drive at all, and may lack any externally accessible 3.5" bays. There are adapters, sometimes called a "sled", which can be used to mount a 3.5" device in a 5.25" bay. New computers rarely have a 5.25 bay and if so often just one but some OEMs may include up to two 5.25 bays and some special custom cases have three (very rare).
More recently, it is becoming common to use 3.5" bays forsmart card andmemory card readers, or for panels with additionalUSB ports. A 3.5" drive containing both a card reader and a floppy drive, as well as a USB port, is also available.
The dimensions of a3.5" drive are specified in the SFF standard specificationsSFF-8300 andSFF-8301, which were incorporated into the EIA-740 specification by the Electronic Industries Association (EIA).[2]
For2.5-inch bays, actual dimensions are2+3⁄4 inches (69.9 mm) wide, between 5 millimetres (0.20 in) and3⁄4 inch (19.1 mm) high, and 3.955 inches (100.5 mm) deep. However, most laptops have drive bays smaller than the 15 mm specification. 2.5-inch hard drives may range from 7 mm to 15 mm in height. There are two heights that appear to be prominent. 9.51 mm size drives are predominantly used by laptop manufacturers.2.5-inch Velociraptor[3] and some higher capacity drives (above 1 TB), are 15 mm in height. The greater height of the 15 mm drives allows more platters and therefore greater data capacities. Many laptop drive bays are designed to be removable trays in which the drives are mounted, to ease removal and replacement.
The dimensions of a2.5-inch drive are specified in the SFF standard specificationsSFF-8200 andSFF-8201, which were incorporated into the EIA-720 specification by the Electronic Industries Association (EIA).
1.8-inch bays have two specifications, a 60 mm × 70 mm form factor, and a 54 mm × 78 mm form factor. The actual dimensions of the 60 mm × 70 mm are 2.75 in wide by 0.276–0.374 in high and 2.362 in deep (69.85 mm × 7–9.5 mm × 60 mm). The actual dimensions of the 54 mm × 78 mm are 2.126 in wide by 0.197 or 0.315 in high and 3.091 in deep (54 mm × 5 or 8 mm × 78.5 mm). These drives have been used in small devices, including as add-ons to game systems historically. This form factor is virtually absent from new computers and laptops due to the preference of 2.5 drives HDDs/SSDs which have a significantly higher capacity and for SSDs the M.2 form factor which is much more compact and can also use thePCIe interface making them much faster thanSATA-based SSDs.
The dimensions of a1.8-inch drive are specified in the SFF standard specificationsSFF-8111 andSFF-8120, which were incorporated into the EIA-720 specification by the Electronic Industries Association (EIA).
Drive bays are most commonly used to storedisk drives, although they can also be used for front-endUSB ports, I/O bays,memory card readers,fans, fan controllers,RAID controllers, tool storage, and other uses. Some computers have a smallsystem monitor LCD mounted in a drive bay.
When installing a drive in a bay, it is usually secured with four screws that hold the drive in the bay, although toolless fasteners are becoming more common. Then, any necessary power, data transfer, and other cables are routed into and connected to the rear of the drive. The drive bay is usually just big enough for the drive to fit inside. Since computers have 12 V rails on their motherboards, some computer hobbyist websites even sell addons forcigarette lighter receptacles to power or recharge devices made to draw power from automobiles, though USB is already available for charging devices likecell phones andportable media players.
Drive bay-compatible computer case accessories that do not connect to the motherboard or power supply at all are also common, such as small storage drawers or evencup holders.
![A 1980s white box IBM PC compatible with one full-height 5.25-inch drive bay containing a half-height 5.25-inch floppy drive[a]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aJET101.JPG)
