PCAN-PCI Express MSI capability depends on the board hardware design, not merely the operating system or host chipset. Evidence confirms that early revision 1.1 prototype cards operated with message-signaled interrupts, while revision 2.1 cards use a Tundra PCIe-to-PCI bridge with the standard PCI CPLD and support only legacy interrupts.
Revision-Dependent Interrupt Support
| Board revision | Reported hardware | Interrupt behavior |
|---|---|---|
| 1.1, April 2007 | Early prototype design using a Lattice FPGA | MSI operated in the reported systems, but the design was discontinued after problems on multiple PCIe platforms. |
| 2.1, September 2008 | Tundra PCIe-to-PCI bridge with standard PCI CPLD | MSI is not supported by either the bridge implementation or the PCI CPLD; the card uses legacy interrupt operation. |
| Later revisions | Not identified in the evidence | No later MSI-capable revision is confirmed. |
Why Revision 2.1 Cannot Be Switched to MSI
The revision 2.1 behavior is a hardware limitation rather than an RTOS driver setting. The bridge-and-CPLD design does not support MSI, so changing driver initialization cannot make that revision generate message-signaled interrupts. Observing INTA operation is consistent with its legacy-interrupt-only design.
Successful Windows operation does not prove MSI capability. In the reported Intel SR2500, Intel SR2600, and HP Z800 installations, the cards could operate under Windows while the real-time environment imposed a separate constraint: legacy interrupts could not be shared between Windows and IntervalZero RTX.
Determine Whether the Card Fits the Host
- Read the physical board revision and identify whether the card is the early FPGA prototype or the later Tundra bridge design.
- Map legacy interrupt sharing for the intended PCIe slot. On the reported SR2600, every PCIe slot except one shared a legacy interrupt with a PCI Express Hub.
- If Windows and RTX must not share a legacy interrupt, reserve the available non-shared slot for a legacy-only card or use hardware that explicitly supports MSI.
- Treat revision 2.1 as incompatible when MSI is mandatory. Do not plan a driver-level MSI workaround for that hardware.
Verification and Procurement Decision
Verify operation by confirming the interrupt mode actually selected by the RTOS driver and checking that the assigned interrupt is not shared across Windows and RTX. For revision 2.1, the expected result is legacy interrupt operation; failure to enter MSI mode is not evidence of a driver defect.
For replacement procurement, require written confirmation of MSI support for the exact board revision and hardware design. The available evidence does not establish that any revision newer than 2.1 restores MSI support, so a revision number alone is insufficient acceptance criteria.
FAQ
Does PCAN-PCI Express revision 2.1 support MSI?
No. Its Tundra PCIe-to-PCI bridge and standard PCI CPLD design supports legacy interrupt operation, not message-signaled interrupts.
Why does a PCAN-PCI Express card work in Windows but fail with RTX interrupt requirements?
Windows operation can use a legacy interrupt. The reported RTX configuration prohibits sharing that legacy interrupt between Windows and RTX, which makes slot interrupt routing and MSI capability decisive.
Is there a PCAN-PCI Express revision newer than 2.1 with MSI support?
The evidence confirms no such revision. Obtain MSI confirmation for the exact hardware revision before selecting a card for a system that cannot use shared legacy interrupts.