Pls help computer will not post unless monitor is off and unplugged

[BigPapaGB]

So i just upgraded my cpu ram and motherboard, went from a i7700k to an i913900k, motherboard is a z790 p wifi and ram is 32 gb g skill trident ddr5 6000. when i set it up between updating the bios and the constant refusal to not post finally got windows to be reinstalled and semi functioning. i have tested both sticks of ram by themselves and can get to the bios just fine when something on the mother board changes it gets to bios on first boot when it stays the same it turns on but monitor will light up and then go black without posting.

after doing some research saw someone suggesting to unplug the monitor and turn on the computer it posts and even boots to windows just fine and i replug the monitor back in and i am good to go any suggestions?

[BigPapaGB]

my current setup:

Intel Core i9-13900K

G.Skill Trident Z5 2X16gb

ASUS TUF Gaming Z790-Plus WiFi

geforce 3080 ti

1tb ssd samsung

just upgraded psu to 1300w evga in hopes that it was a power issue (it was not)

 

Monitor is odyssey g9

 

[PopsicleHustler]

I've had same issue when I purchased 7900XTX. My PC refused to post with DP cable plugged in and monitor off. I found this reddit post that suggested to cover one of the DP cable pins. Have a read for yourself.  It fixed my issue.

 

EDIT: I have same problem, monitor backlight would come on but I got no image and no post.

 

[BigPapaGB]

12 minutes ago, PopsicleHustler said:

I've had same issue when I purchased 7900XTX. My PC refused to post with DP cable plugged in and monitor off. I found this reddit post that suggested to cover one of the DP cable pins. Have a read for yourself.  It fixed my issue.

 

EDIT: I have same problem, monitor backlight would come on but I got no image and no post.

 

thank you i will try it when i get home

[BigPapaGB]

10 minutes ago, micha_vulpes said:

On this same note : I had a system that worked okay, but had a whole bunch of strange issues like lights staying on even when the PC was powered off, or randomly it would trip current protection on the PSU.

When I bench assembled it, what I found was a bad DP cable ( pinned out incorrectly with a conductor on that pin that should be blank). It would back feed enough power into the GPU, and then into the PSU enough to spin the PSU fan...  Even if the PSU was unplugged from the wall.  It is the Wildest thing I have ever seen with modern PC parts

yeah whats weird is this didnt become an issue until 2 days ago when i swapped out the motherboard for a new cpu and ram, im assuming it has to be the motheboard cause there were no issues with the gpu or DP before i swapped the MB i have a replacement MB coming in today to see if its possibly the cmos battery but still im confused as to why it would start when i switched from pcie3.0 to 5.0

[PopsicleHustler]

33 minutes ago, BigPapaGB said:

yeah whats weird is this didnt become an issue until 2 days ago when i swapped out the motherboard for a new cpu and ram, im assuming it has to be the motheboard cause there were no issues with the gpu or DP before i swapped the MB i have a replacement MB coming in today to see if its possibly the cmos battery but still im confused as to why it would start when i switched from pcie3.0 to 5.0

My issue arose when I upgraded from 3090 to 7900xtx. From what I've been able to gather, it's due to newer DP standard on the AMD 7000 GPUs.

 

Some things in custom PC building world are wild to think about.