Error code 26 says, according to this thread
http://www.xtremesystems.org/forums/showthread.php?t=21884026 Reserved/Unused
(but in the manual it says the following: 1. if early_init_onboard_generator is not defined onboard clock generator initialization. Disable respective clock resource to empty PCI & DIMM slots. 2.init onboard PWM 3. init onboard H7W monitor devices)
Error code with the
FIRST gtx installed stopped at FF, this is what is says about FF if you have no picture:
FF booting (from Int 19h) [If the Debug LEDs show FF but the Display stays black, possibly combined with one long and two short beep codes, check the detailled description of POST code 2b on the top]
then on to 2b:
2b
When the system powers on and the Debug LED shows the usual POST code sequence but hangs on 2b or you get a beep code as soon as the sequence reaches 2b, then the Mainboard cant detect your Videocard properly. Note that the POST code sequence might not halt at 2b but continue, so the final POST Code it displays could be FF, 00 or 7F which means the Maiboard booted, entered BIOS, or OC recovery kicked in and is waiting for Input to enter BIOS. Since the Videocard couldnt be detected properly you will only see a black Monitor and either 2b, FF, 00 or 7F. Check if there is something wrong with the Videocard, the PCIE slot or BUS, the Monitor or monitor cable. Turn the Monitor on and off, switch the Monitor cable from one D-SUB or DVI plug to the other in case your Videocard has two. If this doesnt help then reboot and load the optimized defaults. If that doesnt help either try another Videocard if possible, or try the Videocard in another system to make sure its working properly. Try another monitor or try the Monitor on another System.