Question Why might motherboards not acknowledge a specific graphics card?

[Justiceinacan]

Hello

As I've been testing rigs recently I've noticed an odd trend. I've got a Radeon RX 480 8GB reference card, which I've used for a few solid years of gaming in a Gigabyte board, but [older] Asus boards ignore it entirely, and my newest ASRock board only lets it work in the bottom slot.
The exact boards ;
ASUS P8Z68-V PRO : No display
ASUS M5A97-R2.0 : No display
ASRock Z370 Extreme4 : No display in top slot, works fine in bottom slot
Gigabyte GA-78LMT USB3 : works fine
Gigabyte 990FXA-UD3 (Rev 1.0 and R5) : works fine

Why might this be? The card works totally fine in my gigabyte boards, and other cards work fine in the other boards. This reference card is the only GPU that needs to be in a specific motherboard to work.

 

[LinuxDevice]

There is a difference between not registering the card and not having a display.

No display on a working card can often be because the card cannot query the monitor and the mode chosen isn't within the monitor's specs. However, often the monitor will briefly make a note about being out of range.

If your card requires extra power connectors and this isn't provided (or the supply power is insufficient), expect this to occur.

Sometimes BIOS settings won't enable a particular slot.

For an otherwise working system PCIe itself won't always detect a card. PCIe has slower/older revisions and faster/newer revisions. Older revisions are backwards compatible. If during the link training period the faster revision (e..g, rev. 3) has insufficient signal quality, then it will back off to the next slower revision. Eventually, if it gets to the oldest/slowest revision (rev. 1), and if that has insufficient quality, then the PCI bus will not present a card as being present to the operating system. Slots further from the CPU (or PCIe bridge) would tend to have more issues with signal quality than slots close to the CPU.

If you can boot and get into an operating system without the card (for example, perhaps there is an integrated card), you can look at a list of devices visible to the system and find out if the card shows present or not. If not, then something is wrong somewhere along the lines of power delivery or signal quality or BIOS settings for that slot. If the card is present, then more likely the issue is with the query of the monitor via the video card (and to that extent often the problem is with the cable).