d7 dr. debug code

In the meantime, perhaps someone here has experienced a similar issue and can help.

The board is an ASRock x79 extreme7.

CPU is an i7 3930k.

All other parts have been swapped in and out during troubleshooting (see below for details).

The computer works without issue once it reaches the post screen.  Typically it gets stuck on code d7 and never shows a picture.

Sometimes it does work though I cannot pin down what is causing it to post or what is preventing it.

Here are some of the steps I've tried:

Usually I am able to get it to finally go to bios after 5-20 tries clearing cmos. 

I am just at a loss and pretty much willing to try anything.  After the most recent reboot I have spent roughly 1 hour with the system and had no luck.  That has happened before though and when I returned a day later 5-10 tries clearing cmos eventually would get it to post.... so I think the system works.

I will try to compile a list of others codes that the board shows and what steps were taken prior to posting those codes.  

From a troubleshooting standpoint I am stumped and that is pretty rare for me.  Has anyone else ever experienced anything similar or have any ideas?

...And please email me back asrock support.  In the past you have been great which is why I've stuck with asrock boards after switching from gigabyte and asus 10 years ago.

2 wired ps2 keyboards and one ps2 mouse. 

2 wired usb keyboards and 1 wired usb mouse.

and 2 wireless usb keyboards.

All of those input devices work without issue on other systems and all of them work without issue on this system when it posts.

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With that said, I just spent another hour tearing the whole system down cleaning dust and reseated everything connected to the main board.

It did not post again.

It stopped on d7 most of the time.  

However it also is stopping on 6A after every few reboots/cmos clearing.

6A appears to be a memory issue.

Perhaps I didn't seat the ram correctly when i put it back together so I'm going to tear it down again.  Unfortunately with my heatsink I have to remove it to access the 2 dimms closest to the cpu.  I'm going to take all the ram out and put in 2 dimms of different ram.  Unfortunately I don't have another compatible board to put ddr3 in so I can't run memtest on the ram unless I can get past post which is the whole problem...

Still, the system runs without issue until reboot with no hardware changes.  That makes me believe this is a bios issue.  Perhaps compatibility issue with the RAM.  I'll post specs of each set of ram when I return.