In principle, the SH ARC-PCIu is backwards compatible with the SH ARC-PCI. The SH ARC-PCI can only be operated in PCI slots with a 5V supply, while the SH ARC-PCIu is suitable for slots with 5V or 3.3V.
Whether you can replace an SH ARC-PCI with an SH ARC-PCIu without further adjustments therefore only depends on how your software accesses the cards:
1) If your application accesses the card via the SOHARD ARCNET RAW driver, an exchange is possible.
2) If your application addresses the ARCNET controller COM20020 directly, an exchange is also possible. Please note that different system resources (I/Os, memory areas, interrupts) can be assigned to each PCI card.
3) If your application uses a driver that does not originate from SOHARD, we cannot guarantee interchangeability.