Enabling Above 4G Decoding makes the POST and boot process very very slow.

[Raziel49]

Hi there,

I was playing around with my laptop that has i7-8750h and RTX 2070 to see if i could enable the hidden Above 4G Decoding option, hoping that i could enable it for then modifying the bios with ReBAR module.

I can find the variable and activate it, and it kinda works, but upon avctivating the option, the laptop takes ages to post, and when the uefi logo finally appears, it takes another age to begin the process of booting windows. Like 15 minutes in total.

The Above 4G decoding option itself it's working fine - large memory is present in device manager ending with FFFFFFFFF and no errors are shown.

Upon restarting the laptop, it boots up at normal speed. The problem happens again if i shut off the laptop completely, so on "cold" boot.

I just can't understand why it takes so long to start the pc. I have csm disabled and all of that.

Any ideas?

[Raziel49]

i have just observed that sometimes it takes a lot of time to start even if the laptop was only rebooted from already on state.

But happens everytime on "cold" boot.

[jokubasver]

Noticing this as well on Huananzhi X79 v2.49P. Usually it just hangs on the Windows loading circle screen for ages, after multiple reboots it usually gets to boot and works just fine after that. Really annoying though..

Edit: seems like the issue for me was RSTe drivers - I installed a modded, recommended driver version for X79 from the Win-Raid forums, and now seems like everything is fine. While I was at it, I updated the AHCI/RAID EFI/OpROM modules in the BIOS.

Edit 2: turns out, the drivers didn't fix it - boot times are still inconsistant, usually taking a very long time. Switching my boot SSD from SATA 3 6Gbps to the SATA 2 3Gbps port makes the system boot almost instantly, weird...

[Squall-Leonhart]

do not install RSTe drivers, just use the stock msahci driver.