Simcity 4 Directx mode won't work because the game's graphics card compatibility list (Graphics Rules.sgr) requires a hex string to add a new entry as per this guide, which Intel graphics P4600 doesn't have because its integrated, not a discrete card. I have to use software rendering, which works well because the Xeon E3 1225 is such a great CPU, but I can't use mods with HD textures, that requires editing Grahics Rules.sgr, which I can't do because there's no hex string assigned to integrated graphics. Is there a hex string that just won't show up in System Information? If so, what is it? If not, is there a way to trick the game by emulating a discrete card that does have one?
On Intel side, this information is not available through this channel of support. I would recommend waiting for other community member that may have experienced same issue give you details about this matter.