**Peripheral Component Interconnect Express (PCIe)**
  * 1-bit serial bus called lanes
  * Up to 32 independent serial lanes
  * 250 MBps throughput per lane (8 GBps for 32x)
  * Connects directly to the northbridge like AGP
  * PCIe 2.0 doubles the throughput

**Peripheral Component Interconnect (PCI)**
  * Comes in both 32 and 64-bit bus widths
  * 3.3V and 5V volts but mostly 3.3V now
  * Came in 33 and 66 MHz speeds
  * Up to 532 MBps throughput (64-bit, 66 MHz PCI 2.1)
  * Slots are colored white

**Accelerated Graphics Port (AGP)**
  * Used exclusively for graphics cards
  * 32-bit wide data bus
  * AGP bus connects to the northbridge
  * Up to 2.1 GBps throughput (AGP 8x)
  * Multipliers enable AGP devices to operate between bus clock cycles
  * Used multiplier settings of 1x, 2x, 4x, 8x
  * 3.3V, 1.5V, 0.8V depending on AGP revision
  * Slots are typically brown

**Extended Industry Standard Architecture (EISA)**
  * 32-bit wide data bus
  * Found on older ATX and AT motherboards
  * Ran at 8.33 MHz
  * Obsolete

**Industry Standard Architecture (ISA)**
  * 8 and 16-bit wide buses
  * Ran at 4.77 MHz (8-bit) and 6-8 MHz (16-bit)
  * Found on older XT and AT motherboards
  * Obsolete

**Micro Channel Architecture (MCA)**
  * Proprietary interface and bus architecture
  * Used on old IBM PS/2 systems
  * 32-bit wide data bus
  * Up to 66MBps throughput
  * 10 MHz bus speed
  * Obsolete

**Audio/Modem Riser (AMR)**
  * A special expansion slot for audio and modem cards
  * Found on older ATX boards
  * Superseded by CNR

**Communications and Network Riser (CNR)**
  * A special expansion slot for modems and network interface cards
  * Found on some older ATX boards but not new ones
  * Still found on some microATX boards