Is the Z840 compatible with AMD MI50 32GB?

[Jsnowly]

I plan to purchase a Z840 to install two AMD MI50 32GB graphics cards. After testing on a B760 motherboard, I found that the ‘Above 4G Decoding’ feature must be enabled on the motherboard to pass the BIOS self-test and enter the operating system.

However, based on my research, I found that the Z840's BIOS hides the toggle for this feature. Users cannot freely enable or disable this option.

However, any graphics card with over 4GB of VRAM should require this feature to be enabled for proper functionality. The Z840 has explicitly confirmed compatibility with graphics cards like the M6000 24GB, which have over 4GB of VRAM.

Does the Z840 motherboard automatically enable the ‘Above 4G Decoding’ feature after detecting a specific graphics card model? Or does the motherboard automatically enable it whenever the graphics card's VRAM exceeds 4GB?

I am unsure of the logic behind the motherboard's automatic enablement of this feature. Has anyone tried using an AMD MI50 or other models in the same series on the Z840? Do these graphics cards function normally on the Z840?

[DGroves]

the above 4gb decoding bios setting  (when enabled) is poorly understood by most people all it does is allow the memory region that is allocated for mapping the video card's (or any other pci-e card) ram address space to system ram via the pci-e bus to a memory region that is above the computer systems 4GB memory limit

depending on the video card and the specific system, enabling or disabling this option will usually show  a improvement one way or the other there is no one setting fits all possible configurations

in general leaving this setting disabled (which is the default in most systems) has no major impact on video card performance

there are cases where enabling the setting when using a video card and a THunderbolt card or a video capture card can improve performance or allow both cards to function due to the ability of the system now able to move the pci-e cards memory mapping from all under 4gb address space mappings into a higher (above 4gb) memory mapping address

the link below goes into some detail on this bios setting and may be useful to some people

https://www.gameunion.tv/en/games/above-4g-decoding-your-bioss-dark-horse-what-it-and-should-it-be-1...

Edit: i forgot to mention that the AMD MI50 card can draw up to 300 watts and as such using 2 of them will require the upgraded 1125 watt power supply and the optional dual CPU option to enable the white pci-e slots on the motherboard

you will also need 4 of the HP 6 to 8 pin GPU power adapters

 https://www.amazon.com/HP-Power-Supply-Adapter-N1G35AA/dp/B011Z74OGW

i do not recommend other 3rd party adapters due to some of them being poorly made

and keep in mind that the z840 is not windows 11 compatible out of the box due to the cpu generation used

however you can easily install win 11 by using a modified installer that bypasses the CPU/TPM checks