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.
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.