Well, the 3944 and the 4034 BIOSes were the only original BIOSes made for the XBOX v1.0.
However, I have created my own RETAIL BIOS for v1.0 XBOX consoles that contains the 5101 kernel. If you are using a v1.0 XBOX with a retail BIOS, I recommend that you upgrade to my 5101 BIOS. (You can find the link in my signature.)
NOTE: Since my v1.0 5101 BIOS does contain Microsoft code, (the 5101 kernel) you can only find it on XBINS.