Computer case screws are the hardware used to secure parts of a PC to the case. Although there are numerous manufacturers of computer cases, they have generally used three thread sizes. The Unified Thread Standard (UTS) originates from the United States, while the ISO metric screw thread is standardized worldwide. In turn, these thread standards define preferred size combinations that are based on generic units—some on the inch and others on the millimetre.
From left to right: a #6-32 UNC thumbscrew, a #6-32 UNC screw, an M3 screw and a self-tapping screw for case fans
Various types of motherboard standoffs
A male DE-9 connector showing hex jackposts on either side of the D-shell. Note the limited clearance.
Close-up of a #6-32 UNC screw with a flanged hex/Phillips head, commonly provided in PC cases
A motherboard is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.
Dell Precision T3600 System Motherboard, used in professional CAD Workstations. Manufactured in 2012
Motherboard for a personal desktop computer; showing the typical components and interfaces which are found on a motherboard. This model follows the Baby AT (form factor), used in many desktop PCs.
Mainboard of a NeXTcube computer (1990) with microprocessor Motorola 68040 operated at 25 MHz and a digital signal processor Motorola 56001 at 25 MHz, which was directly accessible via a connector on the back of the casing
The Octek Jaguar V motherboard from 1993. This board has few onboard peripherals, as evidenced by the 6 slots provided for ISA cards and the lack of other built-in external interface connectors. Note the large AT keyboard connector at the back right is its only peripheral interface.