I recently found that on my Windows NT V4.00 SP6 system running on an X58 motherboard (ASUS P6T SE) when I called HalGetBusDataByOffset() to read bus 255 the return value was 0 meaning bus does not exist.

On the same system when I boot WXP-x64 or W10-x64 HalGetBusDataByOffset() successfully reads bus 255.

I have tried to Google for the maximum PCI bus supported by NT4 and was unable to find any information. Should HalGetBusDataByOffset() be able to read bus 255 on NT4 and if not what is the limit? It's at least 9.