Serial presence detect Serial presence detect In computing, serial presence detect (SPD) is a standardized way to automatically access information about a memory module. Earlier 72-pin SIMMs included five pins that provided five bits of "parallel presence detect" (PPD) data, but the 168-pin DIMM standard changed to a serial presence detect to encode much more information. When an ordinary modern computer is turned on, it starts by doing a power-on self-test (POST). Since about the mid-1990s, this process includes automatically configuring the hardware currently present. SPD is a memory hardware feature that makes it possible for the computer to know what memory is
Serial communication more specific name, to reduce confusion. Keyboard and mouse cables and ports are almost invariably serial—such as PS/2 port and Apple Desktop Bus and USB. The cables that carry digital video are almost invariably serial—such as coax cable plugged into a HD-SDI port, a webcam plugged into a USB port or Firewire port, Ethernet cable connecting an IP camera to a Power over Ethernet port, FPD-Link, etc. Other such cables and ports, transmitting data one bit at a time, include Serial ATA, Serial SCSI, Ethernet cable plugged into Ethernet ports, the Display Data Channel using previously reserved pins of the