Why would a video card stop a PC from starting

[admiralk]

Long story short: New build, not the latest parts. Turns out swapping a known working card allows the PC to boot. Way past RMA time.

Could this be something simple or is it most likely not worth thinking about?

[magic]

Try different slot, try without other PCIe devices, try after resetting BIOS settings.

[CJay]

PC BIOS 'needs' to see a video card, if it doesn't then it won't complete POST.

As Magic says, take the PC down to bare minimum, try a different slot.

If the PC won't POST with the card in it could be a faulty card or a corrupted video BIOS on the card, you may be able to flash the BIOS on it if the PC boots with the 'faulty' card and a known working second card

[admiralk]

I guess I left out the part where it is completely dead with the card in it. I originally thought it might be a bad psu, but that tested good and then I ran out of time to mess with it. I needed to get a laptop worked on the other day and brought this along for them to check. They told me it ran just fine with a different card, The only other one I have is ancient and might not work anymore anyway. I thought I would just get another card, but they seem to be in short supply right now. I was wondering if maybe there was something I could look for on the card that was keeping it from working. I know it is a long shot, but figured I would ask.

[Nominal Animal]

A short in the card connector in a suitable position can do that.  I do believe I once had a tiny piece of swarf (from the stamped chassis) in a VESA VBE connector cause something similar: the machine would not even turn on.  On PCI Express bus, I guess this could only happen between ground and one of the power pins, but the pinout shows it does have power and ground pins next to each other in more than one spot.  And metal swarf in PC chassises is very, very common: the stamping process often leaves hanging whiskers, that only later detach and drop onto the motherboard..

Internally, PCI Express bus consists of lanes, with serial unidirectional transfers.  The card can garble the operation of the system by sending continuous interrupts (say millions of times per second) or not answering some of the fundamental messages sent, causing the system to "lock up", somewhat as if keeping the system stuck between clock cycles.

It has always been the case on x86 and x86-64 that an expansion card can render the entire system nonfunctional, even stop the CPU from starting (BIOS execution).  Graphics cards especially so, because most BIOSes expect to see one, and won't boot without; they're really not prepared to deal with or even detect a misbehaving graphics card (wrt. bus communications or interrupts etc.).  Because BIOS is on a Flash chip on the motherboard, and all this occurs immediately on power on, way before any OS or boot loader is involved, none of this has anything to do with the OS used at all.

[admiralk]

No obvious problems with the edge connector, so I guess i will just go back to the shop Monday and get the card they used if it has the right port. The KVM switch I have is for DVI. $75 is a whole better than $300 for now.

[Ranayna]

Well, about which components are we even taliking about?
There can be a lot of reasons, especially when the parts are several generations apart.

The card could simply be broken
The BIOS/UEFI does not recognize the card
You did not connect all power connectors
The powersupply is broken

If the system is fully dead with the card, the first and the last are most likely. But please tell us what part you are using so we can do more than just guess.

[DiTBho]

It happened to me when I bought on eBay a MGA card for PC, but I received a MGA card for Mac.
It didn't work. The screen was blank. But it started working as soon as I reprogrammed it.

[DiTBho]

As practical example, The PCI ATI Rage XL

I bought a couple of these cards because I like their simplicity and the source code of the kernel driver, they are PCI32 5V tolerant with 8Mbyte of Video ram and no acceleration, that's exactly the level of simplicity that I need them in a hobby project. My boss was intrigued - will it work in a modern PC with a legacy PCI slot? - she asked - sure - I replied and I lent one card to check it out, but this is  what she said the day after:

"I don't known if if your card was duff or if the model just can't handle UEFI or more recent motherboards, but when I installed the text based boot information was fine, however when the graphical UEFI boot screen appeared, the screen blanked and the monitor reported an out of range error"

Moral of the story

• There are PCI video cards that only work with UEFI (both cards perfectly work in my 2008-old PC)
• I think I need to offer her another dinner to compensate (never say "sure" if you are not 100% "sure")

[admiralk]

That is one reason I do not even try my old card, it is probably from the '90s. My problem card is a GIGABYTE Radeon RX 570. Except it only cost $130. Which should work fine in this MBhttps://www.msi.com/Motherboard/X470-GAMING-PLUS. Picked up the card from the shop that is supposed to work; https://www.msi.com/Graphics-Card/N660-2GD5OC/Specification. Nothing to get excited about, but should get going until I can get another new one. Hopefully I will have time to put it in tomorrow.

[james_s]

Many years ago someone gave me an ISA modem that would prevent the PC from booting. It was an early PnP card and I discovered it had a fault that was causing it to tie up all of the IRQ lines at once. I ended up "fixing" it by sticking tape over the contacts for all but the IRQ I wanted and then I used it for a few years before it failed to the point that it showed up as a COM port but wouldn't respond.

[DiTBho]

Investigating on the ATI, I found a problem: the card normally expects a PC's BIOS to set the reference clock speed for the chip, however, with UEFI this doesn't happen because UEFI has a different procedure for initializing the video card.

My card has a TP, and on the DSO I see the reference clock set to the wrong value.

In my hobby project I can force u-boot to fix the reference clock to the right value, anyway, with a modern PC ... I think this is only one of the problems that prevents a legacy card from operating with UEFI.

[coromonadalix]

In some bios setting you have or had  pci  irq's  choices / assignations, it could lock the bios from starting

nowadays you have the : integrated or external  pci video  settings  or even an pci video card boot options  like the integrated one first and the external second  .....  or an auto mode


Best luck would be  reset the bios / clear cmos,  remove all the sloted cards use the internal video if you cpu  has it ... and redo the video settings ? choose external  boot first

you dont give specs for the motherbaord, cpu,  video card ......... not much to work with