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Do Expansion Units use IRQ

Last Updated: Sep 08, 2016 11:31AM PDT


Do Magma Units use IRQ?



IRQ gets assigned not to the Expansion unit but direclty to the 3rd Party PCI card that gets installed in the Chassis.


Detailed Info:


Cardbus uses a shared IRQ across the cable.  
• The 3rd party PCI cards in the expansion each generate the IRQs when application they are running requires it (code / driver dependant).
• With our Cardbus and PCI-to-PCI, we share one physical signal wire in the cable for all the IRQ’s the expansion bridge implements.  
• They are time multiplexed on this wire; there is the equivalent of a start bit, some delay, then IRQ’s 1,2,3,4, (if present), then some delay, then equivalent of a stop bit.  This is a synchronous with the PCI clock.

PE6R4 uses IRQ’s on the expansion backplane, but the Intel Bridge handles these as it converts the PCI bus protocol into PCIe protocol.
• PCIe is point to point so any IRQ information doesn’t need to be on its own signal wire (ie: IRQ1, IRQ2, IRQ3 ….), instead it is embedded into the PCIe protocol so that the OS / software on the host will see a device generated an IRQ and needs to be serviced.

PCIe by itself does the same thing; there is no IRQ signal wire(s); the IRQ “message�? is embedded into the serial protocol.

From a hardware point of view, there is a difference, from a software point of view, almost none, the OS takes care of routing the “IRQ�? from a device on the PCI bus be it on a PCI slot or PCIe slot, to the CPU.


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