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Now that I’ve
shown how we expose the wire resources, let me show you how we expose the
pins.
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It’s pretty
simple. Routes off the edge of the chip are multiplexed down onto the pins.
This gives
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us 14 7.2
Gb/s channels, for a total of 201 Gb/s of bandwidth in and out of the chip.
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We can hook
up things like PCI buses, DRAMS and antennaes to these I/O ports. In fact,
the problem
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has been
finding I/O devices that can come even close to saturating a channel.
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Now, anyone
can put a bunch of pins on a chip and get bandwidth. The key is that an tile
can toggle an data pin just
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by sending a
message there. That means that we have a mechanism for directly controlling
the I/O resources of the chip.
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This
contrasts with a conventional microprocessor, where it uses all of the pins
solely to slosh cache lines back and forth.
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