Older board wont boot

I have an asrock x79 extreme 9 mobo with socket 2011 intel cpu and 32 g of corsair ram; the machine has performed very well for 4 yrs or more. Lately it started out where it wouldn't catch the boot once in a while and soon I am turning on and off 2 or 3 times to get it to boot and then it wouldn't boot at all.  HD and Power supply checked ok in a diff machine. I have it now where it will boot occasionally but I must have reset cmos because now it goes to Asrock splash screen and it does not respond to the various keyboard commands needed to enter the bios settings. I have even procured a ps2 keyboard and it doesn't work. I guess I need to figure out if its the board, I'm toast as its not readily available now and everything but the video cards are obsolete now... any help will be greatly appreciated.

Yes I have replaced battery

Really frustrated with this, I took everything apart, inspected, cleaned and assembled piece by piece, outside of the case. For the most part it behaved the same as before. only booting every 3rd or 4th time. When it did boot all looks good initially, starts with OCZ boot screen for HD, the keyboard lights up and seems to respond to the key board when it prompts to hit space bar to continue to mobo screens. Then right to the Mobo splash screen; for almost all different types of keyboards, the delete key would generate a beep from keyboard and most of the time the tab key would take you to another Dos looking screen with bios info but no other keys responded at all. I have tried different power supplies and every combination possible of keyboards, PS2, USB, and USB to PS2 converters, 1 stick of memory, 2 sticks and 4 sticks, with OCZ PCI HD in and without. It gives all the normal post beeps if you try to boot with no memory or whatever. It will run for hours on the splash screen; It feels like if I could somehow get by this one keystroke to adjust the boot settings, all would be fine. Even though it is 4 years old, the recent addition of new video cards and  it will max out 7.9 on windows performance index with only one 7.8. I really hate to have to junk this machine. Any other ideas?  Thanks in advance, Don M

I have taken it all apart now; really frustrated but I think when it failed to boot it settled on error code 68 "Pci host bridge initialization". When it does catch a boot and goes to splash screen it displayed 06 "microcode loading". When I take the OCZ pcie drive out and install it in a diff. machine with similar HD it booted to that drive so I don't think its the drive. All other drives and everything else was removed. I have reset cmos with jumpers and button on board.

Thanks again for the help. Here is CPU info: Intel Core i7-3820 Sandy Bridge-E Quad-Core 3.6GHz (3.8GHz Turbo Boost) LGA 2011 130W.  I have never had to mess with the bios or flashed bios previously. I cant really confirm what version is installed now as it wont go past splash screen but more than likely whatever came with the chip in 2012. I never did try to connect a mouse to the board as I figured I wouldn't need it unless it some how booted to windows. I never thought of the mouse as being required for these early boot sequences. The video cards are these: EVGA GeForce GTX 960 02G-P4-2966-KR 2GB SSC GAMING w/ACX 2.0+. I had 2 connected in SLI but have switched to only one for troubleshooting. I have never had any issue with them and have tried switching out between them during troubleshooting. on the last round, I have been working on the board outside of case but it has a reset button on the board; I'm sure ive tried that. I guess it must be the board gone bad...