N2U400-A v1.x maximum CPU and HDD supported information as below,
HDD:400G
CPU: AMD Duron 200Mhz FSB CPU - 950 AMD Duron 266Mhz FSB CPU - 1800
          AMD Morgan 200Mhz FSB CPU - 1.4G
          AMD Athlon 200Mhz FSB CPU - 1.4G AMD Athlon 266Mhz FSB CPU - 1.4G
          AMD Palomino 266Mhz FSB CPU - 2100+
          AMD Athlon XP (0.18u) 266Mhz FSB CPU - 2100+ AMD Athlon XP (0.13u) 266Mhz FSB CPU - 2600+ 
          AMD Athlon XP (0.13u) 333Mhz FSB CPU - 3000+ AMD Athlon XP (0.13u) 400Mhz FSB CPU - 3200+
          AMD Sempron 333Mhz FSB CPU - 2800+

The N2U400-A v1.0 supports 8X ATI 9200 SE 128MB AGP card & it is also backward compatible with 4x AGP card. But the AGP slot is keyed to support only the latest 1.5-volt AGP cards.

Attached below is the latest BIOS for N2U400-A V1.0. It supports dual-channel memory.
Besides, the standard BIOS of this MB has already supported the dual-channel function.

• get_app Download Link

Please update BOIS to N2B19.BIN attached or above version (after 2004/12) to fix this issue.

• get_app Download Link

The N2U400-A only can support AGP 3.0(8X AGP) VGA card.