PCI-X (PCI eXtended) is a computer bus and expansion card standard that enhances the 32-bit PCI Local Bus for higher bandwidth demanded by servers. PCI-X was developed jointly by IBM, HP, and Compaq and submitted for approval in 1998.
PCI-X was needed as some devices, most notably Gigabit Ethernet cards, SCSI controllers (Fibre Channel and Ultra320), and cluster interconnects could, by themselves, saturate the full bandwidth (only 133 MB/s) of the PCI bus. The first solution was to run the 33-MHz PCI bus at double the speed, 66 MHz, effectively doubling the throughput to 266 MB/s. However, machines with multiple high-bandwidth devices still needed more headroom, so additional pins were added to the slot, going from 120 to 184, to form a 64-bit variety. This initially only ran at 33 MHz, basically giving the same maximum throughput of 266 MB/s. Though combined 64-bit, 66-MHz ports had also been implemented, these extensions had been only loosely supported as optional parts of the PCI 2.x standards. Device compatibility beyond the basic 133 MB/s continued to be difficult.
PCI-X was needed as some devices, most notably Gigabit Ethernet cards, SCSI controllers (Fibre Channel and Ultra320), and cluster interconnects could, by themselves, saturate the full bandwidth (only 133 MB/s) of the PCI bus. The first solution was to run the 33-MHz PCI bus at double the speed, 66 MHz, effectively doubling the throughput to 266 MB/s. However, machines with multiple high-bandwidth devices still needed more headroom, so additional pins were added to the slot, going from 120 to 184, to form a 64-bit variety. This initially only ran at 33 MHz, basically giving the same maximum throughput of 266 MB/s. Though combined 64-bit, 66-MHz ports had also been implemented, these extensions had been only loosely supported as optional parts of the PCI 2.x standards. Device compatibility beyond the basic 133 MB/s continued to be difficult.
0 comments:
Post a Comment