Computer Hardware - ISA Slots

This episode is about the history of the computer expansion card slots on the IBM ATX motherboard There have been a number of designs iterations including ISA, PCI and PCI-e ISA (Industry Standard Architecture) was created in 1981 by Mark Dean's team at IBM They riser connectors installed on an ATX motherboard to allow external add on cards to be connected Use of the installed add on card could be both internal and via the back plate of the computer system Cards available for use were very varied including CD player controllers, sound card with game controller ports multiple COMM port cards for modems and remote access via dial in phone number for business and extra communications ports such as SCSI for hard drives or tape backup drives (both internal and external) The riser ports on the motherboard have gone through many design iterations as the communication speeds increased - Starting as black ISA slots, via 2 lengths, a short 8Mbytes/s and a longer 16MB/s, maximum of 6 per motherboard : In 1992 (11 years later) saw an extension called VESA local bus (VLB) introduced to enable high throughput of 66Mb/s for graphics cards to be connected - Then in June 1992 a new generation riser PCI (Peripheral Component Interconnect) was introduced, generally white : Originally running the cards at 5v, a new 3v system came in with a mechanical alteration to stop them being installed in the 5v slot : They were 32bit with speeds of 133 and 266MB/s, a longer slot version called PCI-X was also available in normally in servers and high end PCs : were 64bit and had speeds of 266 and 533Mb/s - 2003 (11 years after PCI and 22 years past the original introduction) saw a new generation called PCI-e (PCI Express) : These had data lanes, hence the x1, x2, x4, x8 and x16, the length of the connector would dictate the lane support : any card would git any port of a higher capacity, an x4 card would fit in to an x8 connector : The version of the PCI-e port would indicate the data through put speed of each lane. version 1 was 0.25Gb/s each lane, an x8 connector was 8 lanes, 0.25 x 8 = 2Gb/s : Each new revision generally almost doubled the lane speed speed: - v1 in 2003 was 0.25Gb/s - v2 in 2007 was 0.5Gb/s - v3 in 2010 was 0.985Gb/s - v4 in 2017 was 1.969Gb/s - v5 in 2019 was 3.938Gb/s - v6 in 2022 was 7.563Gb/s - v7 in 2025 is 15.125 Gb/s - v8 scheduled for 2028 will be 30.25gb/s : v6 PCIe x16 connection would be just over 120Gb/s (7.563Gb/s x 16) Since the introduction PCI and PCIe have a few other connector types not exclusive to add on cards, such as the M.2 connector for hard drives, Bluetooth and WIFI cards, they also adhere to the PCIe version and lane width specifications. M.2 being the connector design (hence why both SATA and PCIe hard drives are available in the M.2 connector format). The high through put of PCI-e is why generally a motherboard only had a single PCIe x16 connector, some higher end PCs and servers would have 2, we have seen a few with 3 connectors : Although one would drop back to x8 lanes if the other 2 had x16 lanes in use