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Infini band
Amdahl's Law is one of the fundamental principles of computer science and
basically states that efficient systems must provide a balance between CPU
performance, memory bandwidth, and I/O performance. At odds with this, is
Moore's Law which has accurately predicted that semiconductors double
their performance roughly every 18 months. Since I/O interconnects are
governed by mechanical and electrical limitations more severe than the
scaling capabilities of semiconductors, these two laws lead to an eventual
imbalance and limit system performance. This would suggest that I/O
interconnects need to radically change every few years in order to
maintain system performance. In fact, there is another practical law which
prevents I/O interconnects from changing frequently - if it am not broke
don't fix it.
Bus architectures have a tremendous amount of inertia
because they dictate the bus interface architecture of semiconductor
devices. For this reason, successful bus architectures typically enjoy a
dominant position for ten years or more. The PCI bus was introduced to the
standard PC architecture in the early 90's and has maintained its
dominance with only one major upgrade during that period: from 32 bit/33
MHz to 64bit/66Mhz. The PCI-X initiative takes this one step further to
133MHz and seemingly should provide the PCI architecture with a few more
years of life. But there is a divergence between what personal computer
and servers require.
Personal Computers or PCs are not pushing the bandwidth
capabilities of PCI 64/66. PCI slots offer a great way for home or
business users to purchase networking, video decode, advanced sounds, or
other cards and upgrade the capabilities of their PC. On the other hand,
servers today often include clustering, networking (Gigabit Ethernet) and
storage (Fibre Channel) cards in a single system and these push the 1GB
bandwidth limit of PCI-X
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