Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

Stratix4GX PCIe development board to used as root port

I wanted to know if anyone has used the Altera Stratix4GX PCIe card as a root port. I have used it as endpoint but have not used as a root- port. As an endpoint all I have to do is plug in t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

You cannot connect your root port in the Stratix4GX with the root port on the motherboard. There must be only/exactly one root complex in the PCIe fabric, just like in PCI where you can also have just one root complex that drives DEVSEL#, etc. Please refer to PCIe Spec Section 1.3 »PCI Express Fabric Topology«.

Again, it’s not possible the way you want it. You can only drive your own, separate PCIe link as a root port as described above: Design a motherboard with your Stratix4GX as the root port, and it will work.

But I’m still not convinced that a root port is what you really want to instantiate. As an endpoint in a PCIe slot, you can act as a bus master and issue DMA transfers on your own, issued by your CPU. But you cannot be another root port. Period.

I cannot help you for the BAR question as I am not into root port design.