6 Expansion slots 45 and there will be some loss of performance Moreover PCI 64

6 expansion slots 45 and there will be some loss of

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46 Chapter 7. Desktop motherboards (a) PCI slots/cards (b) Another view of PCI slots/cards Figure 7.2: 32-bit and 64-bit PCI slots/cards
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7.6 Expansion slots 47 Table 7.2 shows the bus width, bus frequency and bus bandwidth of a PCI and PCI-X slots. PCI bus theoretical maximum bandwidth can be calculated using the following equation: Bandwidth ( MBps ) = frequency ( MHz ) × width ( bits ) 8 (7.1) Exercise 7.6.1 Find out the PCI slot on the motherboard (provided) and answer the following questions. a Identify number of PCI slots on the motherboard. b Identify bus-width (32 bit or 64 bit). c Identify frequency of a PCI bus. You may need to see in the motherboard manual which can be downloaded online. d Calculate theoretical maximum bandwidth of a PCI bus. 7.6.2 PCI Express PCI Express or mostly it is written as PCIe has a different design than PCI and PCI-X bus and it is not backward compatible with any one of them. PCIe is a new standard bus which you find in modern computers and it. PCIe has five different physical slots which is called PCIe x1, x2, x4, x8 and x16 where the number shows serial lanes. For example, x16 has total 16 serial lanes for data transmission and each lane is independent of each other. Figure 7.3a shows three x1 (small white color slots) and one x16 slots (blue color). The more lanes, the more data gets transmitted per given time, see figure 7.3b. Some PCIe cards needs additional power where PCIe slot cannot provide enough power, therefore you see auxiliary PCIe 6-pin or 8-pin connectors coming from the power supply to provide an additional power to a PCIe card. For example, PCIe version 2.0 slot provide wattage to a total of 300 W (75W comes from the slot itself, 150W comes from the PCIe 8-pin auxiliary power from the power supply and 75W comes from a PCIe 6-pin second auxiliary power from the power supply). PCIe has gone through many major revisions which are differentiated by versions, see table 7.2. PCIe version Year launched Transfer rate x1 x2 x4 x8 x16 1.0 2003 2.5 GT/s 250 MB/s 0.50 GB/s 1.0 GB/s 2.0 GB/s 4.0 GB/s 2.0 2007 5.0 GT/s 0.5 GB/s 1.0 GB/s 2.0 GB/s 4.0 GB/s 8.0 GB/s 3.0 2010 8.0 GT/s 1 GB/s 2.0 GB/s 4.0 GB/s 8 GB/s 16 GB/s 4.0 2017 16.0 GT/s 2 GB/s 4 GB/s 8 GB/s 16 GB/s 32 GB/s 5.0 2019 32 GT/s 4 GB/s 8 GB/s 16 GB/s 32 GB/s 63 GB/s 6.0 (in process) 2021 64 GT/s 8 GB/s 16 GB/s 32 GB/s 63 GB/s 126 GB/s Note: x1, x2, x4, x8, x16 are throughput. Throughput are rounded off to the nearest decimal. Transfer rate is expressed in transfers per second instead of bits per second due to the fact that the number of transfer carries overhead bits which do not provide additional throughput. Table 7.2: PCIe link performance
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